Ask PG: Why does HN uses full width while paulgraham.com has limited width?

paulgraham.com is totally exemplary for text formatting. I like to mention it like an incredibly well constrained website design. The best feature is the text width which doesn't exceed 550 pixels. It makes the text extremely well readable, including on mobile devices. And it's actually a column width similar to the one used by paper newspapers.

So why is HN using the full screen width? With a relatively small font, it gets harder to read with a window larger than 1000 pixels. Have there been tests to constrain a bit the width of comments? How was the decision taken to make HN full width?