Ya, discoverability is on the radar, but comes after making the chat actually work.
I think, and someone can correct me if I'm off base with this, that we're in the midst of a migration to a category-based model of chat. So group permissions are 'legacy', and will remain supported probably in a separate branch.
We respect permissions across the board; if you're not able to see a category or group, you won't be able to access the chat (and if someone can demonstrate otherwise, plz let me know about it.)
I haven't been able to repro either of the issues described by @Huey_Le or @LuckyLuke; can you provide me links to where it's happening or repro steps?