--- wp-includes/comment.php	(revision 21779)
+++ wp-includes/comment.php	(working copy)
@@ -504,7 +504,7 @@
  * @param string $meta_key Metadata name.
  * @param mixed $meta_value Metadata value.
  * @param bool $unique Optional, default is false. Whether the same key should not be added.
- * @return bool False for failure. True for success.
+ * @return bool The meta ID on successful update, false on failure.
  */
 function add_comment_meta($comment_id, $meta_key, $meta_value, $unique = false) {
 	return add_metadata('comment', $comment_id, $meta_key, $meta_value, $unique);
--- wp-includes/comment.php	(revision 21779)
+++ wp-includes/comment.php	(working copy)
@@ -504,7 +504,7 @@
  * @param string $meta_key Metadata name.
  * @param mixed $meta_value Metadata value.
  * @param bool $unique Optional, default is false. Whether the same key should not be added.
- * @return bool False for failure. True for success.
+ * @return bool The meta ID on successful update, false on failure.
  */
 function add_comment_meta($comment_id, $meta_key, $meta_value, $unique = false) {
 	return add_metadata('comment', $comment_id, $meta_key, $meta_value, $unique);
--- wp-includes/meta.php	(revision 21779)
+++ wp-includes/meta.php	(working copy)
@@ -96,7 +96,7 @@
  * @param string $meta_value Metadata value
  * @param string $prev_value Optional. If specified, only update existing metadata entries with
  * 		the specified value. Otherwise, update all entries.
- * @return bool True on successful update, false on failure.
+ * @return bool The meta ID on successful update, false on failure.
  */
 function update_metadata($meta_type, $object_id, $meta_key, $meta_value, $prev_value = '') {
 	if ( !$meta_type || !$meta_key )
@@ -160,7 +160,7 @@
 	if ( 'post' == $meta_type )
 		do_action( 'updated_postmeta', $meta_id, $object_id, $meta_key, $meta_value );
 
-	return true;
+	return $meta_id;
 }
 
 /**
--- wp-includes/post.php	(revision 21779)
+++ wp-includes/post.php	(working copy)
@@ -1479,7 +1479,7 @@
  * @param string $meta_key Metadata name.
  * @param mixed $meta_value Metadata value.
  * @param bool $unique Optional, default is false. Whether the same key should not be added.
- * @return bool False for failure. True for success.
+ * @return bool The meta ID on successful update, false on failure.
  */
 function add_post_meta($post_id, $meta_key, $meta_value, $unique = false) {
 	// make sure meta is added to the post, not a revision