As far as I can tell, it’s based on a combination of upvotes and time since posting. New comments start at the top of their tree and, as time passes, settle int

As far as I can tell, it’s based on a combination of upvotes and time since posting. New comments start at the top of their tree and, as time passes, settle into where they would be if sorted by upvotes. So yours is above the other one because it’s more recent, but in a week, if the upvotes don’t change, the other one will be on top. It’s probably a similar algorithm to Reddit’s published “hot” algorithm (http://amix.dk/blog/post/19588 http://amix.dk/blog/post/19588).