There are layers to this.
Does a person say they WOULD do it?
What sort of message would be bad enough to justify making it public?
If I think a person is hair-trigger enough to go off at any message I send, I wouldn't trust them.

Do I think John (sorry about getting personal) is thin-skinned or whiny enough to do that? No. I feel John would reason with me. I think he'd try to understand my point of view and try to help me understand his. If he became frustrated enough to give up, he might tell me to fuck off, after which I'd stop sending him PMs and he'd stop sending me PMs.

I think what John would reveal is different from what others would.
I've had some slightly nasty PMs from people, but haven't even considered inviting anyone else to share. I can't imagine any friend being grateful for me having included them in some private situation which they couldn't do anything about.

I don't think it's smart to, if someone's motive is to get under my skin, let the whole of Mudcat know they've succeeded.