how hard would it be to tell offensive people not to post to each other, or else.
In my experience on SI, easy enough to tell people that but extremely difficult to police it. I remember one poster there who would end up as one of side of multiple bi-lateral posting bans. The bans I used there were that they couldn't post to *or about* each other.
Well, this one poster (there were others, but this one was a prime example) would make veiled comments about the other, then say "No, that wasn't about the other person at all." Or would report perceived veiled comments about them and indignantly demand that person's termination.
That person was frequently surrounded by "Drama" and despite being a friend was also my biggest administrative nightmare for a long time.
Would be nice if we could say "Both of you, pretend the other doesn't exist and never existed or take it elsewhere", but there are always people who must have it their way regardless of the admin's wishes and will try their darnedest to get away with as much as they possibly can. It's almost a game to them.