--- wp-comments-post.php	2008-08-25 10:05:20.000000000 +0200
+++ wp-comments-post.php	2008-08-29 15:09:17.000000000 +0200
@@ -40,6 +40,8 @@
 // If the user is logged in
 $user = wp_get_current_user();
 if ( $user->ID ) {
+	if (empty($user->display_name))	{
+		$user->display_name=$user->user_login;}
 	$comment_author       = $wpdb->escape($user->display_name);
 	$comment_author_email = $wpdb->escape($user->user_email);
 	$comment_author_url   = $wpdb->escape($user->user_url);