How to add a category to comments?

OK, I finally made it following this crystal clear tut

Consequently, my functions.php became:

add_action( 'comment_form_logged_in_after', 'additional_fields' );
add_action( 'comment_form_after_fields', 'additional_fields' );

function additional_fields () {
  echo '<p class="comment-form-title">'.
  '<label for="title">' . __( 'Titre (Je peux...)' ) . '</label>'.
  '<input id="title" name="title" type="text" size="30"  tabindex="5" /></p>';

  echo '<strong><label for="category">Cette solution est particulièrement utile...</label></strong>
    <select id="category" name="category">
        <option value=""></option>
        <option value="Tous">Dans tous les cas</option>
        <option value="Argent">Sans argent</option>
        <option value="Temps">Sans le temps</option>
        <option value="Santé">Sans la santé</option>
    </select>';

}


add_action( 'comment_post', 'save_comment_meta_data' );
function save_comment_meta_data( $comment_id ) {
  if ( ( isset( $_POST['title'] ) ) && ( $_POST['title'] != '') )
  $title = wp_filter_nohtml_kses($_POST['title']);
  add_comment_meta( $comment_id, 'title', $title );
  if ( ( isset( $_POST['category'] ) ) && ( $_POST['category'] != '') )
  $category = wp_filter_nohtml_kses($_POST['category']);
  add_comment_meta( $comment_id, 'category', $category );

}

I hope it’ll help