It's never been a grey area before Puddle. This is the first time there has been any sort of mayhem over a joke thread.
Most of the time Mumsnet governs itself and that's what I like about it. We are self-moderating. Most posters knew when a joke thread came around and those who didn't and got taken in, usually saw the funny side in the end when the poster came clean.
Under your definition they should have been banned, but nobody minded and we all shared a laugh and some classic threads were born.
It would be such a shame if that self-moderation were to end now and we were faced with rigid rules that did not allow for humour, community, shared jokes and fun.
It's a shame that some posters can't let this one be. I fail to see what harm it did and I fail to see why they would want Mumsnet to be so rigidly moderated.
As I said before, what on earth has changed?