I've seen several offers of mobile-optimized CSS for this site over the past while, yet this feels like a half-done job. On my iPhone 5 the margins are all off, the vote icons are still impossibly small, and the header is a mess. It looks like this isn't much more than an added viewport meta tag.

It is still an improvement, but it could be much better. I know the YC crew are busy folks, but you could throw a few bucks to the poster with the best mobile CSS and I'm sure people would be up for the challenge.