I've never seen a proposed redesign that didn't either add too much whitespace or too little (well, always the former), which makes me think that the current design is in the ballpark of optimal, despite its being unfashionable. Also, HN is very much a text site and that goes deeper than look-and-feel. The first thing most "spruce-ups" do is toss this quality, which compromises the site at its essence and indicates a misunderstanding of what HN is. I'm reminded of Steve Jobs' famous line about how design is not how-it-looks but how-it-works.
If someone did a redesign of HN that preserved both its information density and its textiness, I'd be stoked to see it as an experiment. We probably wouldn't change the site much, because if there's one force stronger than user complaints about design, it's user complaints about design changes. Also, I think it's an advantage for HN to have an unfashionable design, and a huge advantage to have a stable design. Still, I'd be fascinated to see it, and there might be ideas we could use.