diff --git a/politeiad/backendv2/tstorebe/plugins/comments/cmds.go b/politeiad/backendv2/tstorebe/plugins/comments/cmds.go
index ebbb5ffc1..a6637c4b5 100644
--- a/politeiad/backendv2/tstorebe/plugins/comments/cmds.go
+++ b/politeiad/backendv2/tstorebe/plugins/comments/cmds.go
@@ -441,9 +441,16 @@ func (p *commentsPlugin) cmdNew(token []byte, payload string) (string, error) {
 		return "", err
 	}
 
+	// Ensure no extra data provided if not allowed
+	err = p.verifyExtraData(n.ExtraData, n.ExtraDataHint)
+	if err != nil {
+		return "", err
+	}
+
 	// Verify signature
 	msg := strconv.FormatUint(uint64(n.State), 10) + n.Token +
-		strconv.FormatUint(uint64(n.ParentID), 10) + n.Comment
+		strconv.FormatUint(uint64(n.ParentID), 10) + n.Comment +
+		n.ExtraData + n.ExtraDataHint
 	err = util.VerifySignature(n.Signature, n.PublicKey, msg)
 	if err != nil {
 		return "", convertSignatureError(err)
@@ -560,9 +567,16 @@ func (p *commentsPlugin) cmdEdit(token []byte, payload string) (string, error) {
 		return "", err
 	}
 
+	// Ensure no extra data provided if not allowed
+	err = p.verifyExtraData(e.ExtraData, e.ExtraDataHint)
+	if err != nil {
+		return "", err
+	}
+
 	// Verify signature
 	msg := strconv.FormatUint(uint64(e.State), 10) + e.Token +
-		strconv.FormatUint(uint64(e.ParentID), 10) + e.Comment
+		strconv.FormatUint(uint64(e.ParentID), 10) + e.Comment +
+		e.ExtraData + e.ExtraDataHint
 	err = util.VerifySignature(e.Signature, e.PublicKey, msg)
 	if err != nil {
 		return "", convertSignatureError(err)
@@ -687,6 +701,17 @@ func (p *commentsPlugin) cmdEdit(token []byte, payload string) (string, error) {
 	return string(reply), nil
 }
 
+// verifyExtraData ensures no extra data provided if it's not allowed.
+func (p *commentsPlugin) verifyExtraData(extraData, extraDataHint string) error {
+	if !p.allowExtraData && (extraData != "" || extraDataHint != "") {
+		return backend.PluginError{
+			PluginID:  comments.PluginID,
+			ErrorCode: uint32(comments.ErrorCodeExtraDataNotAllowed),
+		}
+	}
+	return nil
+}
+
 // cmdDel deletes a comment.
 func (p *commentsPlugin) cmdDel(token []byte, payload string) (string, error) {
 	// Decode payload
diff --git a/politeiad/backendv2/tstorebe/plugins/comments/comments.go b/politeiad/backendv2/tstorebe/plugins/comments/comments.go
index fdd674b27..82f5cd4b4 100644
--- a/politeiad/backendv2/tstorebe/plugins/comments/comments.go
+++ b/politeiad/backendv2/tstorebe/plugins/comments/comments.go
@@ -5,7 +5,6 @@
 package comments
 
 import (
-	"fmt"
 	"os"
 	"path/filepath"
 	"strconv"
@@ -15,6 +14,7 @@ import (
 	backend "github.com/decred/politeia/politeiad/backendv2"
 	"github.com/decred/politeia/politeiad/backendv2/tstorebe/plugins"
 	"github.com/decred/politeia/politeiad/plugins/comments"
+	"github.com/pkg/errors"
 )
 
 var (
@@ -42,6 +42,7 @@ type commentsPlugin struct {
 	// Plugin settings
 	commentLengthMax uint32
 	voteChangesMax   uint32
+	allowExtraData   bool
 }
 
 // Setup performs any plugin setup that is required.
@@ -137,6 +138,7 @@ func New(tstore plugins.TstoreClient, settings []backend.PluginSetting, dataDir
 	var (
 		commentLengthMax = comments.SettingCommentLengthMax
 		voteChangesMax   = comments.SettingVoteChangesMax
+		allowExtraData   = comments.SettingAllowExtraData
 	)
 
 	// Override defaults with any passed in settings
@@ -145,19 +147,26 @@ func New(tstore plugins.TstoreClient, settings []backend.PluginSetting, dataDir
 		case comments.SettingKeyCommentLengthMax:
 			u, err := strconv.ParseUint(v.Value, 10, 64)
 			if err != nil {
-				return nil, fmt.Errorf("invalid plugin setting %v '%v': %v",
+				return nil, errors.Errorf("invalid plugin setting %v '%v': %v",
 					v.Key, v.Value, err)
 			}
 			commentLengthMax = uint32(u)
 		case comments.SettingKeyVoteChangesMax:
 			u, err := strconv.ParseUint(v.Value, 10, 64)
 			if err != nil {
-				return nil, fmt.Errorf("invalid plugin setting %v '%v': %v",
+				return nil, errors.Errorf("invalid plugin setting %v '%v': %v",
 					v.Key, v.Value, err)
 			}
 			voteChangesMax = uint32(u)
+		case comments.SettingKeyAllowExtraData:
+			b, err := strconv.ParseBool(v.Value)
+			if err != nil {
+				return nil, errors.Errorf("invalid plugin setting %v '%v': %v",
+					v.Key, v.Value, err)
+			}
+			allowExtraData = b
 		default:
-			return nil, fmt.Errorf("invalid comments plugin setting '%v'", v.Key)
+			return nil, errors.Errorf("invalid comments plugin setting '%v'", v.Key)
 		}
 	}
 
@@ -167,5 +176,6 @@ func New(tstore plugins.TstoreClient, settings []backend.PluginSetting, dataDir
 		dataDir:          dataDir,
 		commentLengthMax: commentLengthMax,
 		voteChangesMax:   voteChangesMax,
+		allowExtraData:   allowExtraData,
 	}, nil
 }
diff --git a/politeiad/plugins/comments/comments.go b/politeiad/plugins/comments/comments.go
index d74387885..084d3318c 100644
--- a/politeiad/plugins/comments/comments.go
+++ b/politeiad/plugins/comments/comments.go
@@ -34,6 +34,10 @@ const (
 	// SettingKeyVoteChangesMax is the plugin setting key for the
 	// SettingVoteChangesMax plugin setting.
 	SettingKeyVoteChangesMax = "votechangesmax"
+
+	// SettingKeyAllowExtraData is the plugin setting key for the
+	// SettingAllowExtraData plugin setting.
+	SettingKeyAllowExtraData = "allowextradata"
 )
 
 // Plugin setting default values. These can be overridden by providing a plugin
@@ -47,6 +51,10 @@ const (
 	// user can change their vote on a comment. This prevents a
 	// malicious user from being able to spam comment votes.
 	SettingVoteChangesMax uint32 = 5
+
+	// SettingAllowExtraData is the default value of the bool flag which
+	// determines whether posting extra data along with the comment is allowed.
+	SettingAllowExtraData = false
 )
 
 // ErrorCodeT represents a error that was caused by the user.
@@ -99,8 +107,12 @@ const (
 	// does not match the record state.
 	ErrorCodeRecordStateInvalid ErrorCodeT = 11
 
+	// ErrorCodeExtraDataNotAllowed is returned when comment extra data
+	// is found while comment plugin setting does not allow it.
+	ErrorCodeExtraDataNotAllowed = 12
+
 	// ErrorCodeLast unit test only.
-	ErrorCodeLast ErrorCodeT = 12
+	ErrorCodeLast ErrorCodeT = 13
 )
 
 var (
@@ -118,6 +130,7 @@ var (
 		ErrorCodeVoteInvalid:            "vote invalid",
 		ErrorCodeVoteChangesMaxExceeded: "vote changes max exceeded",
 		ErrorCodeRecordStateInvalid:     "record state invalid",
+		ErrorCodeExtraDataNotAllowed:    "comment extra data not allowed",
 	}
 )
 
@@ -151,7 +164,15 @@ const (
 // the deleted comment. Everything else from the original comment is
 // permanently deleted.
 //
-// Signature is the client signature of State+Token+ParentID+Comment.
+// PublicKey is the user's public key that is used to verify the signature.
+//
+// Signature is the user signature of the:
+// State + Token + ParentID + Comment + ExtraData + ExtraDataHint
+//
+// Receipt is the server signature of the user signature.
+//
+// The PublicKey, Signature, and Receipt are all hex encoded and use the
+// ed25519 signature scheme.
 type Comment struct {
 	UserID    string       `json:"userid"`    // Unique user ID
 	State     RecordStateT `json:"state"`     // Record state
@@ -178,7 +199,15 @@ type Comment struct {
 // CommentAdd is the structure that is saved to disk when a comment is created
 // or edited.
 //
-// Signature is the client signature of State+Token+ParentID+Comment.
+// PublicKey is the user's public key that is used to verify the signature.
+//
+// Signature is the user signature of the:
+// State + Token + ParentID + Comment + ExtraData + ExtraDataHint
+//
+// Receipt is the server signature of the user signature.
+//
+// The PublicKey, Signature, and Receipt are all hex encoded and use the
+// ed25519 signature scheme.
 type CommentAdd struct {
 	// Data generated by client
 	UserID    string       `json:"userid"`    // Unique user ID
@@ -206,7 +235,13 @@ type CommentAdd struct {
 // additional fields to properly display the deleted comment in the comment
 // hierarchy.
 //
-// Signature is the client signature of the State+Token+CommentID+Reason
+// PublicKey is the user's public key that is used to verify the signature.
+//
+// Signature is the user signature of the:
+// State + Token + CommentID + Reason
+//
+// The PublicKey and Signature are hex encoded and use the
+// ed25519 signature scheme.
 type CommentDel struct {
 	// Data generated by client
 	Token     string       `json:"token"`     // Record token
@@ -240,7 +275,13 @@ const (
 // CommentVote is the structure that is saved to disk when a comment is voted
 // on.
 //
-// Signature is the client signature of the State+Token+CommentID+Vote.
+// PublicKey is the user's public key that is used to verify the signature.
+//
+// Signature is the user signature of the:
+// State + Token + CommentID + Vote
+//
+// The PublicKey and Signature are hex encoded and use the
+// ed25519 signature scheme.
 type CommentVote struct {
 	// Data generated by client
 	UserID    string       `json:"userid"`    // Unique user ID
@@ -261,7 +302,15 @@ type CommentVote struct {
 // The parent ID is used to reply to an existing comment. A parent ID of 0
 // indicates that the comment is a base level comment and not a reply commment.
 //
-// Signature is the client signature of State+Token+ParentID+Comment.
+// PublicKey is the user's public key that is used to verify the signature.
+//
+// Signature is the user signature of the:
+// State + Token + ParentID + Comment + ExtraData + ExtraDataHint
+//
+// Receipt is the server signature of the user signature.
+//
+// The PublicKey, Signature, and Receipt are all hex encoded and use the
+// ed25519 signature scheme.
 type New struct {
 	UserID    string       `json:"userid"`    // Unique user ID
 	State     RecordStateT `json:"state"`     // Record state
@@ -283,7 +332,15 @@ type NewReply struct {
 
 // Edit edits an existing comment.
 //
-// Signature is the client signature of State+Token+ParentID+Comment.
+// PublicKey is the user's public key that is used to verify the signature.
+//
+// Signature is the user signature of the:
+// State + Token + ParentID + Comment + ExtraData + ExtraDataHint
+//
+// Receipt is the server signature of the user signature.
+//
+// The PublicKey, Signature, and Receipt are all hex encoded and use the
+// ed25519 signature scheme.
 type Edit struct {
 	UserID    string       `json:"userid"`    // Unique user ID
 	State     RecordStateT `json:"state"`     // Record state
@@ -306,7 +363,13 @@ type EditReply struct {
 
 // Del permanently deletes all versions of the provided comment.
 //
-// Signature is the client signature of the State+Token+CommentID+Reason
+// PublicKey is the user's public key that is used to verify the signature.
+//
+// Signature is the user signature of the:
+// State + Token + CommentID + Reason
+//
+// The PublicKey and Signature are hex encoded and use the
+// ed25519 signature scheme.
 type Del struct {
 	State     RecordStateT `json:"state"`     // Record state
 	Token     string       `json:"token"`     // Record token
@@ -329,7 +392,13 @@ type DelReply struct {
 // original upvote. The public key cannot be relied on to remain the same for
 // each user so a user ID must be included.
 //
-// Signature is the client signature of the State+Token+CommentID+Vote.
+// PublicKey is the user's public key that is used to verify the signature.
+//
+// Signature is the user signature of the:
+// State + Token + CommentID + Vote
+//
+// The PublicKey and Signature are hex encoded and use the
+// ed25519 signature scheme.
 type Vote struct {
 	UserID    string       `json:"userid"`    // Unique user ID
 	State     RecordStateT `json:"state"`     // Record state
diff --git a/politeiawww/api/comments/v1/v1.go b/politeiawww/api/comments/v1/v1.go
index b2eda3328..fc2d3a0fa 100644
--- a/politeiawww/api/comments/v1/v1.go
+++ b/politeiawww/api/comments/v1/v1.go
@@ -141,7 +141,15 @@ const (
 // information for the deleted comment. Everything else from the original
 // comment is permanently deleted.
 //
-// Signature is the client signature of State+Token+ParentID+Comment.
+// PublicKey is the user's public key that is used to verify the signature.
+//
+// Signature is the user signature of the:
+// State + Token + ParentID + Comment + ExtraData + ExtraDataHint
+//
+// Receipt is the server signature of the user signature.
+//
+// The PublicKey, Signature, and Receipt are all hex encoded and use the
+// ed25519 signature scheme.
 type Comment struct {
 	UserID    string       `json:"userid"`    // Unique user ID
 	Username  string       `json:"username"`  // Username
@@ -167,7 +175,13 @@ type Comment struct {
 
 // CommentVote represents a comment vote (upvote/downvote).
 //
-// Signature is the client signature of the State+Token+CommentID+Vote.
+// PublicKey is the user's public key that is used to verify the signature.
+//
+// Signature is the user signature of the:
+// State + Token + CommentID + Vote
+//
+// The PublicKey and Signature are hex encoded and use the
+// ed25519 signature scheme.
 type CommentVote struct {
 	UserID    string       `json:"userid"`    // Unique user ID
 	Username  string       `json:"username"`  // Username
@@ -186,7 +200,13 @@ type CommentVote struct {
 // The parent ID is used to reply to an existing comment. A parent ID of 0
 // indicates that the comment is a base level comment and not a reply commment.
 //
-// Signature is the client signature of State+Token+ParentID+Comment.
+// PublicKey is the user's public key that is used to verify the signature.
+//
+// Signature is the user signature of the:
+// State + Token + ParentID + Comment + ExtraData + ExtraDataHint
+//
+// The PublicKey and Signature are hex encoded and use the
+// ed25519 signature scheme.
 type New struct {
 	State     RecordStateT `json:"state"`
 	Token     string       `json:"token"`
@@ -227,7 +247,13 @@ const (
 // upvoted, the resulting vote score is 0 due to the second upvote removing the
 // original upvote.
 //
-// Signature is the client signature of the State+Token+CommentID+Vote.
+// PublicKey is the user's public key that is used to verify the signature.
+//
+// Signature is the user signature of the:
+// State + Token + CommentID + Vote
+//
+// The PublicKey and Signature are hex encoded and use the
+// ed25519 signature scheme.
 type Vote struct {
 	State     RecordStateT `json:"state"`
 	Token     string       `json:"token"`
@@ -248,7 +274,13 @@ type VoteReply struct {
 // Del permanently deletes the provided comment. Only admins can delete
 // comments. A reason must be given for the deletion.
 //
-// Signature is the client signature of the State+Token+CommentID+Reason
+// PublicKey is the user's public key that is used to verify the signature.
+//
+// Signature is the user signature of the:
+// State + Token + CommentID + Reason
+//
+// The PublicKey and Signature are hex encoded and use the
+// ed25519 signature scheme.
 type Del struct {
 	State     RecordStateT `json:"state"`
 	Token     string       `json:"token"`