Hacker News is about preserving its culture and maintaining a high signal to noise ratio, as well as avoiding the Eternal September effect. It isn't a space for free organic discussion, it's a space for curated, thought provoking discussion.
Conversation here is steered and controlled aggressively on multiple levels in the name of quality control, including making it purposely easy for the crowd to censor anything they want, for any reason.
Think of it less as your local pub and more the water cooler at work, except HR posted a lengthy policy about water cooler conversations on the wall, which seems to get longer every week, and the boss is always glancing out of his office, and everything you say around that water cooler goes into your performance review. Also sometimes you'll find the water doesn't dispense but only for you, because apparently that's dependent upon a metric you weren't aware of and at some point you fell under the threshold and were never told but from now on you just have to stand there holding your empty cup like a shmuck.
I don't know what the "pub" equivalent of HN is. I don't think it exists and if it does it's probably already infested with incels and edgelord tools.