diff --git a/wp-includes/feed-atom-comments.php b/wp-includes/feed-atom-comments.php
index e7c3c7cba..9b533fcd4 100644
--- a/wp-includes/feed-atom-comments.php
+++ b/wp-includes/feed-atom-comments.php
@@ -66,11 +66,20 @@ if ( have_comments() ) : while ( have_comments() ) : the_comment();
 		<id><?php comment_link(); ?></id>
 		<updated><?php echo mysql2date('Y-m-d\TH:i:s\Z', get_comment_time('Y-m-d H:i:s', true), false); ?></updated>
 		<published><?php echo mysql2date('Y-m-d\TH:i:s\Z', get_comment_time('Y-m-d H:i:s', true), false); ?></published>
-<?php if (!empty($comment_post->post_password) && $_COOKIE['wp-postpass'] != $comment_post->post_password) : ?>
+<?php if ( post_password_required() ) : ?>
 		<content type="html" xml:base="<?php comment_link(); ?>"><![CDATA[<?php echo get_the_password_form(); ?>]]></content>
 <?php else : // post pass ?>
 		<content type="html" xml:base="<?php comment_link(); ?>"><![CDATA[<?php comment_text(); ?>]]></content>
 <?php endif; // post pass
+	// Return comment threading information (http://www.ietf.org/rfc/rfc4685.txt)
+	if ( $comment->comment_parent == 0 ) : // This comment is top level ?>
+		<thr:in-reply-to rel="<?php the_guid() ?>" href="<?php the_permalink_rss() ?>" type="<?php bloginfo_rss('html_type'); ?>" />
+<?php else : // This comment is in reply to another comment
+	$parent_comment = get_comment($comment->comment_parent);
+	// The rel attribute below and the id tag above should be GUIDs, but WP doesn't create them for comments (unlike posts). Either way, its more important that they both use the same system
+?>
+		<thr:in-reply-to rel="<?php echo get_comment_link($parent_comment) ?>" href="<?php echo get_comment_link($parent_comment) ?>" type="<?php bloginfo_rss('html_type'); ?>" />
+<?php endif;
 	do_action('comment_atom_entry', $comment->comment_ID, $comment_post->ID);
 ?>
 	</entry>