I actually like Hacker News' condensed retro web look. It has a very lightweight bare metal feel to it. I am not really a fan of designs that have "foofy" margins which make the noise to signal ratio higher.
You also seemed to be suggesting that it had something to do with separating different stories on the same page.
My point about separate stories is that it is independent of them. Magazines and newspapers layout their stories in columns. I was anticipating someone saying "Yes, but they also show multiple stories on one page." But magazines and newspapers still use narrow columns of text even when they have a single story on the page.