Tangent:
An (early?!) version of HN source code is available on GitHub [1]. It comes with a custom LISP dialect, ARC, that is itself running under MzScheme.
This architecture looks pretty arcane. Has anyone an idea what lead Paul, et. al. to write a custom LISP dialect for building a web forum? Is that a common thing for schemer's to do to get things done? Or does the ARC language predate the HN implementation? I am not sure.
Someone can correct me if I'm wrong but AFAIK Hacker News was meant to be a MVP for the Arc language itself.
Also a more up to date version of the Arc forum can be found at https://arclanguage.org, and there is a public fork, Anarki at https://github.com/arclanguage/anarki which is not in feature parity with the former, which itself is not in feature parity with Hacker News.