(It's been suggested that this might be a duplicate of this question. It's not: I didn't want to see the upvote/downvote tally (although this would have resolved my confusion!), I wanted an explanation for deducted points. Another user with the same confusion would not be likely to find the linked question.)
I answered this question a day or so ago, engaged in lots of interaction with the OP, and finally expanded my answer to include a little extra yesterday. Today I find my "Achievements" have a "-2" associated with this question. There are no downvotes in sight. Can someone explain the point-loss?
I want to be clear: I don't think I'd change anything about my answer, but if I'm missing something about the rules, I'd like to know it. It's a little like the 1970s, when you could drive across a state line in the US into a state that didn't have a "right turn on red" law, and suddenly be doing something stupid and dangerous without knowing it. If I'm that person, I'd like to know. :)