The part I didn't mention is that community feeds will be separate feeds, and if you are in such a feed, you see all the notes in that community, not just the ones of people you follow. That I'm pretty settled on.

It's really a question of how you go about finding a community, and I thought showing in-community posts in your following feed was a good way to do it, as long as you can subsequently opt-out of communities you aren't interested in.