I'm sorry to say that if you rubbed it on a CD and it didn't scratch, you are doing the test wrong. Even my highest quality microfiber scratches CDs! The "proper" IMHO way to do this test is rub it UNTIL it scratches. Count how many strokes it takes. High quality stuff should take a while . . . it is very relative, I can't give you a number.
Then rub something that you know for a fact is paint-safe (high qual microfiber like neatitems or YoSteve.com) and see which takes more passes to scratch.
This does NOT mean that it wont scratch your paint. The credible use of this test is that it tells you what will scratch LESS.
Nicsands scratched the heck out of CD's in my experience . . . rub it a bit harder than you would rub your car so that you know you will be safe.