Board Thread:Support Requests - Getting Technical/@comment-5578690-20131009230101/@comment-4519283-20131010004151

It depends what you mean. If you mean remove a block or chat ban by allowing that user to continue to edit and/or use chat, then yes. If you mean erase the action so that noone will know that you banned or blocked the user, no. It's technically possible for staff to do it, and it is theoretically possible for administrators to hide it using JS (which would get them in huge trouble), but highly unlikely.