I've seen this argument made quite a bit but I suspect it's overblown. Only pg could answer for certain, but from what I understand, the site is essentially a test application for the language it's implemented in (Arc). I think it's more likely that pg simply didn't find the frontend interesting, so he put as little effort into it as he felt necessary.
I would also question the validity of the assumption that aesthetics and mindlessness are necessarily correlated. If anything, a better looking Hacker News would just have fewer people complaining about its surface flaws.
Not to second guess someone else's motivations, but I would have to disagree. To me, current HN design feels perfect, and I'm sure if pg had wanted it to be "shinier" he would have done so. After all, it's implemented in the language that makes everything else look like Blub, so it would have been easy. HN epitomizes the substance over style school of design.
I would also question the validity of the assumption that aesthetics and mindlessness are necessarily correlated. If anything, a better looking Hacker News would just have fewer people complaining about its surface flaws.