wp_blacklist_check

				$max_length = (int) $col_length['length'];

				if ( ! empty( $col_length['type'] ) && 'byte' === $col_length['type'] ) {
					$max_length = $max_length - 10;
				}
			}

			if ( $max_length > 0 ) {
				$lengths[ $column ] = $max_length;
			}
		}
	}

	/**
	 * Filters the lengths for the comment form fields.
	 *
	 * @since 4.5.0
	 *
	 * @param int[] $lengths Array of maximum lengths keyed by field name.
	 */
	return apply_filters( 'wp_get_comment_fields_max_lengths', $lengths );
}

/**
 * Compares the lengths of comment data against the maximum character limits.
 *
 * @since 4.7.0
 *
 * @param array $comment_data Array of arguments for inserting a comment.
 * @return WP_Error|true WP_Error when a comment field exceeds the limit,
 *                       otherwise true.
 */
function wp_check_comment_data_max_lengths( $comment_data ) {
	$max_lengths = wp_get_comment_fields_max_lengths();

	if ( isset( $comment_data['comment_author'] ) && mb_strlen( $comment_data['comment_author'], '8bit' ) > $max_lengths['comment_author'] ) {
		return new WP_Error( 'comment_author_column_length', __( '<strong>Error</strong>: Your name is too long.' ), 200 );
	}

	if ( isset( $comment_data['comment_author_email'] ) && strlen( $comment_data['comment_author_email'] ) > $max_lengths['comment_author_email'] ) {
		return new WP_Error( 'comment_author_email_column_length', __( '<strong>Error</strong>: Your email address is too long.' ), 200 );
	}

	if ( isset( $comment_data['comment_author_url'] ) && strlen( $comment_data['comment_author_url'] ) > $max_lengths['comment_author_url'] ) {
		return new WP_Error( 'comment_author_url_column_length', __( '<strong>Error</strong>: Your URL is too long.' ), 200 );
	}

	if ( isset( $comment_data['comment_content'] ) && mb_strlen( $comment_data['comment_content'], '8bit' ) > $max_lengths['comment_content'] ) {
		return new WP_Error( 'comment_content_column_length', __( '<strong>Error</strong>: Your comment is too long.' ), 200 );
	}