I check up post history if I feel someone is arguing for the sake of it or arguing in bad faith. Some people's post history is them being contrarian with everyone.

There are also people who act like assholes whilst pretending to represent a group they want to malign. For example after being called a woman hater and misogynist out of the blue I checked the person's history and they go through subs making absurd "feminist" stances that are just to make feminists seem unreasonable. I mean I've argued with actual feminists before, but you look at their post history and they are actually engaged in topics and subs in constructive ways. Even if I don't agree with them on a specific thing you can see that their position is consistent and that they are invested. The one I'm talking about took contrarian positions to anyone, usually with the most unreasonable stances, presumably so people walk away with a negative impression of feminism.