I also believe that Hacker News runs on a small stack of services developed by some past companies from Y Combinator.

I would agree that there is also little to no desire to make Hacker News "the news place" - where it supports thousands of posts a second and is extremely popular. In general Hacker News is used (and the hope is to stay that way) by startups and people interested in startups - it's slowly growing out to include more types of people - marketing, companies, blog posts who just want a lot of hits, etc - and not many people want to purposely support that.