I do know a couple of very successful people who aren't that smart but are good at selling themselves/their ideas. Some people look down on this, but it is a good skill to have.
HN has a problem where the people who comment are often not that knowledgable but can sound like they know what they're talking about. This is particularly bad in posts asking for advice. Allowing downvoting (HN didn't always have it IIRC) actually makes this problem worse. Also for some emotionally charged topics people will downvote true things that make them feel bad.