It's actually against eBay policy to try to figure out who left what DSR, or to "question" a buyer about a DSR (that's the actual wording of it in the user agreement - "question" the buyer).

With that said, you can get around it by wording your message to the buyer carefully (eg: don't ask a question).

One of my buyers left me a 1 for item description awhile ago. Our messages went like this:

Me: "I can see that you have left me a DSR of 1 for item description"

Them:  "yes, the item was smaller than I thought."

Me: "The dimensions of the item are in the description, though."

Them: "You can have eBay remove it if you want."

So I contacted eBay . . . and they gave me the spiel about not being allowed to question buyers about a DSR. I pointed out that I didn't actually "question" the buyer. They removed the low DSR and I received no penalty.