BuddyPress.org

No way of subscribing to topics on these

boards. There was a way to mark it as favoriite but I don’t think that sent any emails on new posts.

You can add custom achievement plugins with the current release. You have to know how to code, though. In the Achievements release that comes out once BP 1.1 is out, site admins will be able to add simple achievements via the admin interface.