Interesting, I thought the feed was just based on chronology + votes! How quaint of me. Is there anything written anywhere about how the feed algorithm works generally?
The feed has always been based on more than just time and votes. For example, flags. Another factor is HN's anti-abuse software, like the voting ring detector. Then there is moderation. For example, moderators downweight certain kinds of stories, such as sensational ones or indignant ones, that routinely attract many more upvotes than others. Another example is the boosting system that was discussed recently here: https://news.ycombinator.com/item?id=19871809.
There's no article or essay about it, but I've posted many comments to HN about all of this over the years. None of it is secret, and we're happy to answer questions.
Are all sites deemed political down-weighted equally? Is this a manually curated list or also algorithmically determined somehow?
Are there other categories / topics that sites might be placed in that affect their ranking?
The problem of trying to apply weights to domains and/or specific submissions based on some idea of how well they fit the ethos of the site seems like an interesting one!
Some of this is algorithmically determined and some of it is manually curated. The more complicated a decision is (e.g. is site X primarily political), the less likely it is to be algorithmic.