You could add your own banner that makes it clear what the status and expectations of the project are. In fact, that is probably a valuable thing to do if the project is archived too.

If you archive it, then sure user's are less likely to send you disrespectful messages by whatever means (assuming they can find such means), but they are also less likely to use it, because you have basically said "this project is abandoned". Which if you don't want users at all, I guess that's fine, but then I'm curious why you bothered to publish it publicly at all.