Fixed typo in

static $allowed_actions = array(
		'delete',
		'CommentsForm',
		'doPostCommentz'
	);

to

static $allowed_actions = array(
		'delete',
		'CommentsForm',
		'doPostComment'
	);

code/controllers/CommentingController.php

@@ -9,7 +9,7 @@ class CommentingController extends Controller {
 	static $allowed_actions = array(
 		'delete',
 		'CommentsForm',
-		'doPostCommentz'
+		'doPostComment'
 	);
 
 	private $baseClass = "";