Index: registration.php
===================================================================
--- registration.php	(revision 6744)
+++ registration.php	(working copy)
@@ -207,6 +207,9 @@
  * If $userdata does not contain an 'ID' key, then a new user
  * will be created and the new user's ID will be returned.
  *
+ * Updates the user's past comments with the new display name,
+ * email address, and URL, if changed.
+ *
  * If current user's password is being updated, then the cookies
  * will be cleared.
  *
@@ -218,6 +221,8 @@
  * @return int The updated user's ID.
  */
 function wp_update_user($userdata) {
+	global $wpdb;
+
 	$ID = (int) $userdata['ID'];
 
 	// First, get all of the original fields
@@ -232,6 +237,10 @@
 		$userdata['user_pass'] = wp_hash_password($userdata['user_pass']);
 	}
 
+	// Update user data in the comments if display name, email, or URL has changed
+	if ( ($user['display_name'] != $userdata['display_name']) || ($user['user_email'] != $userdata['user_email']) || ($user['user_url'] != $userdata['user_url']) )
+		$wpdb->query("UPDATE $wpdb->comments SET comment_author = '{$userdata['display_name']}', comment_author_email = '{$userdata['user_email']}', comment_author_url = '{$userdata['user_url']}' WHERE user_id = '$ID'");
+
 	// Merge old and new fields with new fields overwriting old ones.
 	$userdata = array_merge($user, $userdata);
 	$user_id = wp_insert_user($userdata);