HN user pg, aka Paul Graham, the (co-)founder of both this site, i.e. HN, and YC itself, the "parent" site, was probably the guy (or one of his early colleagues) who implemented the karma feature here on HN.

I am saying this because the feature has been there from pretty early on.

No need to believe me, go verify it yourself, by any means you choose.

And see:

https://en.m.wikipedia.org/wiki/Karma

https://commons.m.wikimedia.org/wiki/File:EndlessKnot03d.png