@since: bbPress (r5156)
Description
bbp_buddypress_add_notification()

Hooked into the new reply function, this notification action is responsible for notifying topic and hierarchical reply authors of topic replies.

Source: bp-forums/notifications.php:181

bbp_notify_forum_subscribers()

Sends notification emails for new topics to subscribed forums

Source: bp-forums/common/functions.php:1238