Non conosco ancora bene WP, questo codice si trova in include/comment-template.php ho provato cambiare il numero del maxlength, volevo sapere se questo è sufficiente o se bisogna mettere un filtro anche in php.
Codice PHP:
$fields = array(
'author' => '<p class="comment-form-author">' . '<label for="author">' . __( 'Name' ) . ( $req ? ' <span class="required">*</span>' : '' ) . '</label> ' .
'<input id="author" name="author" type="text" value="' . esc_attr( $commenter['comment_author'] ) . '" size="30" maxlength="245"' . $aria_req . $html_req . ' /></p>',
'email' => '<p class="comment-form-email"><label for="email">' . __( 'Email' ) . ( $req ? ' <span class="required">*</span>' : '' ) . '</label> ' .
'<input id="email" name="email" ' . ( $html5 ? 'type="email"' : 'type="text"' ) . ' value="' . esc_attr( $commenter['comment_author_email'] ) . '" size="30" maxlength="100" aria-describedby="email-notes"' . $aria_req . $html_req . ' /></p>',
'url' => '<p class="comment-form-url"><label for="url">' . __( 'Website' ) . '</label> ' .
'<input id="url" name="url" ' . ( $html5 ? 'type="url"' : 'type="text"' ) . ' value="' . esc_attr( $commenter['comment_author_url'] ) . '" size="30" maxlength="200" /></p>',
);