form#commentform p.comment-notes {
display: none;
}

function change_formfields($veri) {
$veri['title_reply'] = __( 'Cevapla' );
$veri['comment_notes_before'] = '<p class="comment-notes">Açıklama</p>';
return $veri;
}

add_filter('comment_form_defaults','change_formfields');