and found it again:
commenting line 256 (in facebook.php in the facebook pluginfolder)
// add_filter( ‘comments_array’, array( ‘Facebook_Comments’, ‘comments_array_filter’ ), 10, 2 );
// add_action( ‘wp_enqueue_scripts’, array( ‘Facebook_Comments’, ‘css_hide_comments’ ), 0 );
still searching for an easy and good solution go merge facebook and wp comments.