WordPress at a glance
function is not described

WP_Query::is_comments_popup() WP 3.1.0

Deprecated in 4.5.0. It is no longer supported and can be removed in future releases. It is recommended to replace this function with the same one.

Whether the current URL is within the comments popup window.

This is a method of the class: WP_Query

No Hooks.

Return

true/false.

Usage

$WP_Query = new WP_Query();
$var = $WP_Query->is_comments_popup();

Code of WP Query::is comments popup: wp-includes/class-wp-query.php WP 5.2

<?php
public function is_comments_popup() {
	_deprecated_function( __FUNCTION__, '4.5.0' );

	return false;
}