It would be very nice if you could wrap the post time in a <time> element. I've been toying with the idea of writing a userscript for HN, and it'd be much nicer if I didn't have to parse the post times by hand. Not to mention that right now it's impossible to know the exact time of older comments when they might all say "300 days ago". You could also add a feature to the site itself that would show the exact time and date of a post when you hover over the post time.