Index: wp-includes/feed-rss2-comments.php
===================================================================
--- wp-includes/feed-rss2-comments.php	(revision 6168)
+++ wp-includes/feed-rss2-comments.php	(working copy)
@@ -40,7 +40,7 @@
 		<link><?php comment_link() ?></link>
 		<dc:creator><?php echo get_comment_author_rss() ?></dc:creator>
 		<pubDate><?php echo mysql2date('D, d M Y H:i:s +0000', get_comment_time('Y-m-d H:i:s', true), false); ?></pubDate>
-		<guid><?php comment_link() ?></guid>
+		<guid isPermaLink="false"><?php comment_guid() ?></guid>
 <?php if (!empty($comment_post->post_password) && $_COOKIE['wp-postpass'] != $comment_post->post_password) : ?>
 		<description><?php _e('Protected Comments: Please enter your password to view comments.'); ?></description>
 		<content:encoded><![CDATA[<?php echo get_the_password_form() ?>]]></content:encoded>
Index: wp-includes/feed.php
===================================================================
--- wp-includes/feed.php	(revision 6168)
+++ wp-includes/feed.php	(working copy)
@@ -76,6 +76,19 @@
 
 }
 
+function comment_guid() {
+	echo get_comment_guid();
+}
+
+function get_comment_guid() {
+	global $comment;
+
+	if ( !is_object($comment) )
+		return false;
+
+	return get_the_guid($comment->comment_post_ID) . '#comment-' . $comment->comment_ID;
+}
+
 function comment_link() {
 	echo get_comment_link();
 }