What is the point of mentioning this here as opposed to, say, e-mailing the authors?

With -- at most -- a handful of exceptions (assuming maybe ajacoutot or bapt show up), no one here on HN has the ability to fix this so I really don't see the point.

Also, I guess he gave up shortly after.

There's way more than the single typo ...

Yeah, I noticed that and that's part of the reason I asked. If one pointed out every typo in this document (as well as all other HN submissions), the signal-to-noise ratio of the comments section would be intolerable.

I am counting on the authors seeing this thread.