Index: includes/core/functions.php
===================================================================
--- includes/core/functions.php	(revision 4796)
+++ includes/core/functions.php	(working copy)
@@ -292,7 +292,7 @@
  * @return bool|array $usernames Existing usernames. False if no matches.
  */
 function bbp_find_mentions( $content = '' ) {
-	$pattern   = '/[@]+([A-Za-z0-9-_\.@]+)\b/';
+	$pattern = apply_filters( 'bbp_find_mentions_pattern', '/[@]+([A-Za-z0-9-_\.@]+)\b/' );
 	preg_match_all( $pattern, $content, $usernames );
 	$usernames = array_unique( array_filter( $usernames[1] ) );