I don't hate them, actually, though LOL@www's summing up. I think an exclude from active convos button is a good suggestion. But not just for AIBU - for lots of other topics too.
Becuase I can think of plenty of other topics that get a full share of 'trivial' discussions (for me) ie chat, style, crafts, recipe and TV threads. And all those threads, including AIBU can also attract interesting, funny discussions. Even if I don't find a thread interesting I can see that other people do (and that happens plenty of times). I don't do card making, camping or dinner party cooking but know they mean a lot to other people. So who's to say what is boring and trivial to everyone else here? And actually I have seen plenty of good discussions in the AIBU topic and often look there if I am doing a catch up.
And anyway I like triviality sometimes - doesn't everyone? Ignore what you don't like or start an 'interesting in your opinion' discussion in the AIBU topic. I have seem plenty of them.
Mumsnet talk is what you make it. It is NOT down to the structure of the discussion topic list (in my opinion).
I don't think the AIBU topic is a place for dull peple to hang out. So I certainly don't agree with you aitchtwooh when you say " what a lot of (dull) people seem to want is to be told that they are right to be feeling irritated/wounded etc"
In fact I find that sentiment a bit offensive.