/**
 * Displays an extra text area for more comments.
 *
 * @param int $post_id The ID of the post where the comment form was rendered.
 */
function wporg_more_comments( $post_id ) {
	echo '<p class="comment-form-more-comments"><label for="more-comments">' . __( 'More Comments', 'your-theme-text-domain' ) . '</label> <textarea id="more-comments" name="more-comments" cols="45" rows="8" aria-required="true"></textarea></p>';
}

add_action( 'comment_form', 'wporg_more_comments' );