hybrid havoc on Nostr: I would say that unless you have a rule that the post is in clear violation of, you ...

I would say that unless you have a rule that the post is in clear violation of, you let it be.

If the post is reported by many other users (particularly users of your instance) then perhaps reach out to the poster and ask to CW, and consider whether you want to add something to the rules.

While I don't think moderation and the rules have to be a 1:1 tit-for-tat (which just promotes Rules Lawyering), there should be something applicable if you want to take action.