Fixes per review

Embolden "This change is irreversible"

release-1.6/release-notes-draft.md

@@ -9,8 +9,8 @@ migration of data between different storage engines.  You must stop the API
 from writing to etcd during an etcd2 -> etcd3 migration.  HA installations cannot
 be migrated at the current time using the official kubernetes procedure.
 
-1.6 will also default to protobuf encoding if using etcd3.  This change is
-irreversible.  To rollback, you must restore from a backup made before the
+1.6 will also default to protobuf encoding if using etcd3.  **This change is
+irreversible.**  To rollback, you must restore from a backup made before the
 protobuf/etcd3 switch, and any changes since the backup will be lost.  As 1.5
 does not support protobuf encoding, if you roll back to 1.5 after upgrading to
 protobuf you will be forced to restore from backup, and you will lose any changes