Groups. I almost did it again.......

I understand that groups are somewhat privet yet the threads appear in latest threads.
Some groups get, shall we say a bit touchy, if a non group member posts to one of their threads.
This week I accidentally posted to one group's thread. It was actually a supportive response. None the less I was duly chastised.
OK, I respect their right to allow only their own opinions.

What would be nice is if their would be a way to lock yourself out of posting/responding to any group you don't belong to.

A switch would be nice. Something like Group Append = NO.
Yes I know, that would take some code. I think it would also save others some embarrassment.
I try to be as non offensive as possible however if I do offend someone I'd rather it be by intent rather than by accident.