WordPress antispam. Disable html in comments

// Quick solution that should do the job for dummy bots.

function html_is_bad( $approved , $commentdata )
{

  if($commentdata['comment_content']!==strip_tags($commentdata['comment_content']))
    return 'spam';

  return $approved;
}

add_filter( 'pre_comment_approved' , 'html_is_bad' , '99', 2 );