I don't know understand why its going down? The downvotes should be displayed separately and should not affect the upvotes, unless the upvotes are getting deleted (by somebody or by the upvoters themselves)
You can cause the same thing to happen to any comment by rapidly clicking the upvote button. This seems to cause the upvote count to drift upward, even though you would expect it to just oscillate between two values. I've just taken parkermoseyondown's comment from 0 to 40 upvotes.
Edit: This seems to be a UI issue. After reloading his comment is sitting at only 1 upvote.
Hrm, I'll be fascinated to know whether there's a COS employee of the Atlantic or whether they give moderator accounts to their advertisers, HuffPo-style.