The source code used to be open, and it isn't clear what happened to it. Maybe ask over on the arclanguage.org forum as HN is written in arc.
The closest thing to a source repo is this from many years ago: https://github.com/wting/hackernews
The closest thing to a source repo is this from many years ago: https://github.com/wting/hackernews
Community-supported version: http://arclanguage.github.io
One can hope, though.
Which is to say, the community of users! (You all are awesome... usually)
Also (personal theory of mine) maybe the code doesn't have the degree of abstraction or separation of concerns necessary to allow open sourcing without also exposing YC business concerns or parts they want to keep secret.
> A version of HN's source code is included with the public release of Arc, but HN's algorithm has many extensions that aren't public.
https://news.ycombinator.com/item?id=13456306
> We're unlikely to publish all that because doing so would increase two bad things: attempts to game the site, and meta nitpicking.
Including at least at one time a Chrome extension for moderation:
So security by obscurity helps at times.
Usually, some numbnut "programmer" sets a no-login and a simple password as a secret service account. It invariably is found, and badness ensues.
Whereas login/password is a 1/password_space chance of getting it. It's the combination of a default hidden account and no way to know/change it.
Having the full list of banned keywords, or even acknowledging there is a list, could cause drama. And it's easily evaded if people know about it, like when reddit banned "Tesla" posts got through by misspelling it "Telsa".
There's also other stuff like a controversy filter, that detects articles with more comments than votes and penalizes them. I try to avoid commenting in articles that are getting close to the limit to avoid triggering it.
The HN frontpage algorithms used to be more predictable, now it's a black box.