I would guess people regularly create sockpuppet/throwaway accounts to talk about politics. Too much reputational risk to discuss political topics in the open these days...
And it's an opportunity to say what I really think, without being judged by HN's faux-politeness criteria.
There's such a large intersection between tech and politics these days, in terms of their effects on each other, that the HN aversion to discussing politics just seems anachronistic and ill-judged.
However it doesn’t seem that humans have figured out how to effectively navigate our differences in the more ideological aspects of governance on a forum like this. Just think of how many times in a personal conversation you are happy to respond with nothing more than a ‘yes, but why?’ vs the same topic being discussed on HN or reddit? Or how much more information is exchanged in the ambience of that moment vs words on a page (and it’s still difficult). Online it’s nearly impossible and what you’re left with are echo chambers and vollies of insults.
For my part I appreciate the wet blanket thrown on those types of conversations on HN. I just haven’t seen them yield fruit elsewhere and i appreciate the harbor.