HN runs an evolved version of said "demo of a lisp". So it's probably not the actual code running anymore, but it is a predecessor.
Hacker News literally is (or began as) pg's demo of Arc Lisp.
But Anarki no longer resembles what's running on HN currently.
Never knew! Thank you. Do you know if the current algorithm is published anywhere or do they keep that under wraps to prevent it from being gamed?
I think dang has mentioned they might consider publishing some of the changes they've made over the years but that it would be difficult to untangle the YC business logic from everything else, and they wouldn't have the time to maintain it.
But anything to do with voting, spam detection, ranking etc. though, they definitely keep secret.
dang has mentioned several times the algorithm has evolved over the years.