If the manufacturer permits dry firing of a particular firearm I see nothing wrong with it as long as permission is granted by the seller. Dry firing a brand new revolver, especially with a blued finish, may be frowned upon in an attempt to keep the cylinder turn ring to a minimum.
As stated in previous posts, I've seen people, sellers and purchasers, do some pretty stupid stuff in their attempts to impress others with their handling abilities. Spinning the cylinder and slamming it shut, using the slide lock to drop the slide on an empty chamber, slamming a magazine home "Magnum P.I." style to name a few. Watching them is like watching a train wreck; you want to close your eyes and turn away but you can't.