Plotinus, it's not as "wildly unlikely" as you think. Some people are victims of cyberbullying and stalkers. This is the sort of thing that might happen in such cases; indeed, I have seen it happen on another forum.So the scenario is that someone who has nothing to do with this site, is not a member, and has never posted here, inexplicably decides to cause havoc by registering and imitating someone who is a member?
I think we'll cross that bridge when we come to it.
Seriously, the purpose of this thread is not to ask tortuous casuistic questions about what we'd do in wildly unlikely situations. The title Frequently Asked Questions ought to give a clue to that. It's meant to be for asking useful questions in order to help people use the site.