/**
  * To link to bbPress/BuddyPress profile or also link
  * avatar, see http://blog.samelh.com/?s=comment+author
  */

add_filter('get_comment_author_link', 'se_link_comment_to_archives');
function se_link_comment_to_archives( $link ) {
    global $comment;
    if ( !empty( $comment->user_id ) && !empty( get_userdata( $comment->user_id )->ID ) ) {
   		$link = sprintf(
   			'<a href="%s" rel="external nofollow" class="url">%s</a>',
   			get_author_posts_url( $comment->user_id ),
   			strip_tags( $link )
   		);
    }
    return $link;
}