Ask HN: “A good story to repost”

I received this today by courtesy of HN's repost experiment:

Hi there,

   <URL> looks good, but didn't
   get much attention. Would you care to repost it? You can do so
   by clicking here: <REPOST URL>.

   Please use the same account (hliyan), title, and URL. When these match,
   the software will give the repost an upvote from the mods, plus we'll
   help make sure it doesn't get flagged.

   This is part of an experiment in giving good HN submissions multiple
   chances at the front page. If you have any questions, let us know.

I'm wondering: is this determined by a human mod or an algorithm. If it's an algorithm, I'd be very interested in knowing what type of natural language processing is involved in determining whether HN will like a story!