Nowadays, threads are full of nastiness, with some aibu posters seemingly taking great pleasure in staying just the right side of the guidelines, and the guidelines are fixed - you can't say "fuck off"; you can say "I feel sorry for your children". The result is threads becoming sneery and nasty, rather than being straight up discussions.
I agree with that. There was always, um, heated debate, but the particular brand of nastiness on AIBU now is different. I've been on here since 2007, on and off, and though people were staggeringly rude at times, it was usually over something, not just because. The difference is huge in how the site feels, because the "ick" factor in watching someone barrel into AIBU with the sole intention of being as nasty as they can manage, whatever the topic, is really different to someone losing their rag over a subject that means a lot to them. I often disagreed with people in the latter situation, even thought them bonkers at times, but at least it wasn't spite for the sake of it. It was genuine, sincere belief underlying a lot more of the aggro that surfaced, I think.
I also think there's less accountability, just because the site is so massive. I've got the mind of a fruitfly, so maybe this is just me, but when I was first here, you recognised at least 70% of the names inside a month or two. Now, I hardly recognise any. And that's not namechanging, it's size of site. If people know they will have social consequences, even of the online type, they will usually behave with a bit more integrity. When it's an enormous churning torrent of posts, that doesn't hold true. The anonymity isn't just of a username, and a changeable one at that - it's of too many usernames for many to really register that much, I think. So any residual accountability is lost, unless someone actually cares enough to make an effort to talk to the few they recognise.
The first couple of years I was on here, the site went dead at 11 or so, because unless you had a new baby, you went to bed then so you could cope with the kids in the morning. It was almost solely British, and almost solely parents with dependent-aged kids. Now from all sorts of people, of all ages, from all over the world post, at all times. While that has benefits, obviously, it does also make for a far more anonymous experience.