This made me laugh out loud. I too forget this little website is run by an enormous Venture Capital firm.
It’s really only the plaintext styling that contributes to the humble appearance.
That was so creative of them.
The tech behind the scenes is pretty advanced though, from what I've read. (At least compared to reddit, along with apparently pretty good bot detection and such.)
I don't think it's "run by" the YCombinator. If I recall correctly, YCombinator pays for HN costs, in exchange for 3 things: recruitment posts, YCombinator new startups posts, and having alumni see each others as orange.