Sometimes, when a climate-denial comment on HN seems especially troll-like, and when I have time to kill, I'll look at the comment history of the apparent troll.

Occasionally the person's comments only include political opinions, but I would say that, for the majority of these posters, the technical/programming comments outweigh the political ones.

I don't know about other discussion boards. HN is the only forum on which I actively participate -- maybe because it's so good at self-policing that the trolls don't tend to survive long here.