it seems like, within "top level" comments with the same number of points, the comments switch between sorting ascending and descending by... a staggering of the time posted.

having more points puts you at the top of the comment list.

So, for example, this comment will have one point when i first post it. Since it's the latest comment, it will at first display topmost. When the next person posts a comment, my comment will display last and his will display first. Then when I refresh mine will display first and his last.