WordPress at a glance
function is not described

_clear_modified_cache_on_transition_comment_status() WP 4.7.0

Clear the lastcommentmodified cached value when a comment status is changed.

Deletes the lastcommentmodified cache key when a comment enters or leaves 'approved' status.

No Hooks.

Return

Nothing (null).

Usage

_clear_modified_cache_on_transition_comment_status( $new_status, $old_status );
$new_status(string) (required)
The new comment status.
$old_status(string) (required)
The old comment status.

Code of clear modified cache on transition comment status: wp-includes/comment.php VER 5.1.1

<?php
function _clear_modified_cache_on_transition_comment_status( $new_status, $old_status ) {
	if ( 'approved' === $new_status || 'approved' === $old_status ) {
		foreach ( array( 'server', 'gmt', 'blog' ) as $timezone ) {
			wp_cache_delete( "lastcommentmodified:$timezone", 'timeinfo' );
		}
	}
}