How do I remove, ban, or unban a user from my community?
Neither of these mentions a (very) little-known feature of ban_set -- hiding a community that one is a member of from being listed on the profile in the list of communities, in the same way that a banned user is not listed. Posting access is still shown.
This came up in suggestions, where none of us thought it could be done at all. Much to my surprise, I tested it to prove it wouldn't work, and it did. Notice that I am a member of teatest, but it is not listed on my profile in the appropriate place.
I don't know if it belongs in either of those FAQs, but I'd think it would be a better for for 20 than 84.
Hiding Community Membership
If you do not wish that a community that you are a member of be listed in the community section of your friends on your profile, you can ban that community from the admin console in the same way you would ban a regular user. You can still post to the community, make comments in the community, and receive replies to comments you have made in the community.
If you have access to post in the community, the community will still show up on your posting access list. The community will still appear on your friends list. (You can also hide a community from others viewing your friends page.)