I will tell you that it's mostly the ones you expect if you're heavily engaged with Reddit and moderation. But there are several new gathering places that I didn't know about until we started spelunking on the most annoying posters histories.

This is one of the places where a tool that scrapes reddit and lets you see deleted comments is absolutely clutch--these people are very good about removing the worst of their vile spewing on reddit, or changing their comments to look innocuous after people have gotten worked up. It's all about making people they disagree with look like bullies and idiots.