I think it's sort of a textual fist-bump to people who smile when they see n followed by n/2, because it means something's about to get logarithmic, and we like that.
On a related note, here's how to abuse the concept of URL shorteners in order to produce messages in which embedding a URL costs zero additional characters:
even easier, every 64 characters are 64 bits, simply strtolower all the characters then make the '0' bits lowercase... No typos needed, still plenty of space.
Maybe use a magic pattern in the first few characters to indicate a url ID is present.
He also recently used "orthogonal" in an essay when it really wasn't the best word choice. When given the option to maximize eloquence, the author favors impressing the reader with his technical know-how, sacrificing being articulate for upping his nerd cred. Possibly a smart move for communicating with the HN community and securing his status as leader. A political thing. I often find myself talking more nerdy than I need to in #startups, for example.