I find it's a helpful way to challenge oneself. Get into an argument and very quickly you'll find things you hadn't considered, and a wonderfully easy way to bring one's own tribalism to the surface, where it can be killed more easily.
Getting challenged on one's positions and reconsidering them is ideal if it were so, and perhaps on HN it is about half the time.
On other social media there is no challenge to one's positions. You are racist, so it doesn't matter what you said. You are sexist, so it doesn't matter what you said. You are a shill, so it doesn't matter what you said.
