View file themes/default/templates/system/pages/comments_reply.phtml

<?php
/**
 * @var string $message
 * @var string $max_length
 * @var string $action_url
 * @var string $code
 * @var string $bb_codes
 */

$this->layout(
    'system::layout/default',
    [
        'title'      => $title,
        'page_title' => $page_title ?? $title,
    ]
);
?>

<?php if (! empty($data['message_form'])): ?>
    <div class="mb-3">
        <?= $data['message_form'] ?>
    </div>
<?php endif; ?>

<?php if (! empty($data['back_url'])): ?>
    <div>
        <a href="<?= $data['back_url'] ?>"><?= $data['back_url_name'] ?></a>
    </div>
<?php endif; ?>