One thing I want to clarify is that even though these users are still listed as members of the channel, users who are removed from staff or any other group cannot see channels to which they’ve lost access, and they cannot see or send messages within those channels.
It’s still misleading though, and we have this at the top of our list.
We’re going to get to it soon, and we plan to take the time it requires to sort through the various cases that may exist where users’ access and membership to channels may need to be removed.