Ok, the submission link was originally not a direct link to the PDF. A moderator changed the link, so my comment is now useless, and hence should be deleted. But mysteriously I've lost the ability to edit or delete it, even though it was posted just 16 minutes ago. New HN feature? Maybe the edit time is now reduced from 2 hours to 10 minutes? Not sure.

You were downvoted in that period, which might have something to do with it (people are seriously overzealous about that)