Buffing...is it bad?

frost

Swirl marks in clear coat as visible because light reflects through them. Buffing levels out the clear coat so light doesn't reflect through. You can remove enough clear coat by buffing that will be bad for the paint. Experienced detailers know how to do this properly, but a person who goes to the store and buys a buffer could potentially end up removing too much clear coat, resulting in various issues such as fading and oxidation.