BuddyPress.org

The bpc categories can be hierarchial like you describe Anointed. All content in bpc is a tree of either containers (tags and categories) or content items. Containers can have child containers. Categories are containers. So categories can have child categories like you describe.

The current user interface just doesn’t do that. I’m working on the docs for bpc right now. The next release will be a programmer’s version with all the classes and functions documented. People will be able to create whatever they want.