I, too, found your question very interesting, so I did some research. First, you need to remember two words: 1. "inversion." When the words are NOT in regular order. For example: "Did you eat?" is an inverted sentence. The regular order would be "You did eat." 2. "exclamation." When you want to show EMOTION. For example: "What a beautiful day it is!" ***** 3. Which sentence shows more emotion? a. Boy, he could get on your nerves sometimes. b. Boy, could he get on your nerves sometimes. (Some people would use an exclamation mark. Here is an example that I found: "God, was I hungry!") ***** 4. Books have different terms to describe your sentence, but I found that many experts would label it as an INVERTED EXCLAMATIVE / EXCLAMATION. ***** 5. Here is an example that I have made up: TOM: Can Alice speak French? MONA: Can she ever! = Yes, she really can speak French very well.

Well, you are right. It's a sort of emphatic form, but I have no idea of the grammatical name. It does look like a question. Man, could he ask good questions. <emphasis word>, could he verb. Man, can he ski. Boy oh boy, can he play ball. Crickey, does he sing well. . Anyone know what it's called, I'd also be interested to know.