I was surprised to see my question downvoted. I care less about the loss of rep than about why the person might have done it. Can you find anything wrong with the question? Do you think the person didn't like my presumption that "DD's" is a convention, instead of mere style?
Could be that your question reads as if the apostrophe-based usage is correct/acceptable.
I have seen questions being down voted simply because they were duplicate of other questions; in other cases, the question was down voted because the user didn't like it.
In this specific case, I cannot say which reason would be more plausible.
I didn't downvote your question, but for the mention, I tend to downvote heavily. Well, I don't feel too bad about it, as I think it's how the good questions rise to the top, and how bad questions go down to be forgotten and never displayed again. Lots of people vote, it's common for a question to get 5 upvotes, so one downvote is not the end of the world. It's the a big part of the way other users can give feedback, other than flagging for various reasons.