Source

File: wp-includes/comment.php

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 );
	}

	return true;
}