Commenting probably bothers me the least on a list of things I think are bad about the internet. Comments are one of the few places you can still read about topic X and then see "well, here's topic Y". This is about the only thing making the internet a world wide web and not a world wide expanse of tiny unconnected islands. Search engines are not effective at making these connections anymore, and AI makes the connection but hides it.

As for the worst thing, I think it's that you can have "kittens playing" and "terrorist attack" posts right next to each other. That can't be a good way to view what's going on.