comment_form() unter WP3.0 konfigurieren? Hook funktioniert nicht

<?php
class TTT_Comment_Form
{
    public
        // Name und E-mail Pflichtfelder?
        $req
        // Der aktuelle Kommentator, Daten awerden aus dem Cookie gelesen.
    ,   $commenter
        // Kann frei erweitert werden um weitere Optionen.
    ,   $options  = array (
            'textarea_first' => TRUE
        )
        // Code der Textarea, falls sie versetzt wird.
    ,   $textarea = ''
    ;


    /**
     * Setzt die Ausgangswerte.
     * @param array $options
     */
    public function __construct( $options = array () )
    {
        $this->req       = (bool) get_option( 'require_name_email' );
        $this->commenter = wp_get_current_commenter();


        $this->options = array_merge($this->options, $options);


        add_filter(
            'comment_form_default_fields'
        ,   array ( $this, 'filter_default_fields' )
        );
        add_filter(
            'comment_form_defaults'
        ,   array ( $this, 'filter_defaults' )
        );


        if ( function_exists('show_subscription_checkbox') )
        {
            add_action('comment_form_after', 'show_subscription_checkbox');
        }


        if ( $this->options['textarea_first'] )
        {
            add_action( 'comment_form_top', array ( $this, 'print_textarea') );
        }
    }


    /**
     * Gibt die Textarea separat aus.
     * @return void
     */
    public function print_textarea()
    {
        print $this->textarea;
        return;
    }


    /**
     * Filtert einzeilige Felder.
     * @param  array $f
     * @return array
     */
    public function filter_default_fields($f)
    {


        $f['author'] = '<p><label for="author">Name'
            . ( $this->req ? ' *' : '' )
            . '</label> '
            . '<input id="author" name="author" type="text" size="30" value="'
            . esc_attr( $this->commenter['comment_author'] ) . '"'
            . ( $this->req ? ' required' : '' )
            . '></p>';
        $f['email'] = '<p><label for="email">E-Mail'
            . ( $this->req ? ' *' : '' ) . '</label> '
            . '<input id="email" name="email" type="email" value="'
            . esc_attr(  $this->commenter['comment_author_email'] ) . '" size="30"'
            . ( $this->req ? ' required' : '' ) . '></p>';
        $f['url'] =  '<p><label for="url">Website</label> '
            . '<input id="url" name="url" type="url" value="'
            . esc_attr( $this->commenter['comment_author_url'] )
            . '" size="30" /></p>';


        return $f;
    }


    /**
     * Filter die ganzen kleinen Strings im Formular.
     * @param  array $d
     * @return array
     */
    public function filter_defaults($d)
    {
        // unset () würfe eine Fehlermeldung, weil der WP-Code das
        // nicht prüft.
        $d['comment_notes_after']  = '';
        $d['label_submit']         = 'Absenden';


        $name                      = trim($this->commenter['comment_author']);
        $d['title_reply']          = ( isset ( $name[1] )
                                    ? "Hallo $name! " : '' )
                                    . 'Was sagst du dazu?';




        $d['comment_notes_before'] = $this->req
            ? '' : 'Nur das Textfeld ist Pflicht.';
        $d['comment_field']        = '<p><label for="comment">'
            . 'Kommentar</label><textarea id="comment" name="comment" cols="50" rows="15" required></textarea>
        </p>';


        if ( $this->options['textarea_first'] )
        {
            $this->textarea = $d['comment_field'];
            unset ( $d['comment_field'] );
        }


        return $d;
    }
}