public static function subscribe($event, $type, $entity) {

		if (!$entity instanceof Comment) {
			return;
		}

		$original_container = $entity->getOriginalContainer();
		if (!$original_container instanceof \ElggObject) {
			// Let core subscriptions deal with it
			return;
		}

		if (check_entity_relationship($entity->owner_guid, 'comment_tracker_unsubscribed', $original_container->guid)) {
			// User unsubscribed from notifications about this container
			return;
		}

		add_entity_relationship($entity->owner_guid, 'comment_subscribe', $original_container->guid);
	}