Can we hide users?

I would like a way to hide a user (temporarily, probably). Like, have their posts not show up in threads, have them not show up in member list, etcetera. Some forums have a feature to do this that's associated with banning spammers or something, but I couldn't find anything for "show this user's posts to other people" as an option. I can create a new usergroup, or permissions, or whatever if that is the right way to do it.

I don't actually care whether or not they can still post, I just want a way to let them disappear. It would actually be sorta cool if users could set it for themselves.