On this question (the question is irrelevent, I'm just stating when I noticed this and where it happened) Convert String to Enum? I accidently upvoted an answer that I thought didn't deserve an upvote. The score of the answer was at the time 0.
After I upvoted, the answer went to +1. Obviously. I then realized my mistake, and downvoted the question because I wanted to take back my upvote.
The question's score went from +1 to -1 (a total of 2 points!) And I did not believe that the question deserved -1. Is this a bug? Shouldn't you be able to subtract from +1 to go back to 0?