The one mildly annoying thing that might be a user error on my point is that if I swipe into the community selector menu, I'm stuck. I haven't figured out how to get back to where I was.
Do you mean, can't find your place in the post feed?
One thing I recommend for users that scroll really far in the feed is to use post hiding (with the hide button enabled in the feed - or auto hide). That way you won't lose your place, even if the app restarts. Of course you can reset hidden posts too.
No. If I scroll all the way to the left so that I get to the page where I can select from my subscribed communities, all, local etc. by mistake. Then I cannot get back to what ever feed I swiped away from. If I try to swipe right again I end up unsubscribeing to some unlucky community.
Also, it would be nice to get an undo option in the notification toast you get for unsubscribeing to a community if possible. I just lost one without noticing which one while recreating my issue for this reply.