"I'm not interested" and "Don't show posts from this person" is the dowvote button for the algorithm. If you use those functions liberally your feed gets pretty clean and aligned.
Except here on HN, other people take care of the downvoting for me. I only have to reach for the downvote button a few times a year.
Whereas on Facebook style algorithmic feeds, you have to "use those functions liberally" and the result is only "pretty" clean.
I used to belong to a FB nostalgia group that was being relentlessly farmed by Indonesian accounts. The group members (and even the admins) weren't sophisticated enough to spot what was happening. They were absolutely engaging with the spam. They love AI colorizations too.
I don't trust "facebook users" as a group to provide a signal I consider useful.
HN model works, people do downvote for you, if you are just like everybody else here. You indicate that by visiting HN.
In more universal platform such as Facebook you need to indicate who you are by subscribing to specific groups or downvoting some of the content yourself. Just visiting. Facebook is not enoug. Once you signal who you are you also benefit from other people just like you downvoting content you wouldn't like, for you.
This is what is so difficult in facebook vs. HN. Here if people post angry insulting rants, it gets collectively downvoted to oblivion. That is effective.
On facebook there is no equivalent. All I can do is block an individual, but I personally have to do it for every offensive person, which is for practical purposes impossible. Facebooks needs a downvote button and an option to hide any comments which have N downvotes.