Not exactly on topic, but the biggest usability flaw in HN is the inability to minimise a post (and its child comments), coupled with no hiding of child comments a million levels deep (this I'm fine with, if you could hide posts). Having to scroll down half a page to see what other discussions are happening around a link really blows.
I agree, it's utter garbage. If only HN had some sort of a voting system where users could vote for the comments they like and the most liked comments would float to the top.