If you don't want the reseller or a future purchaser to be able to look you up, just use an engraving tool and cover the number up. If you don't want to do that, you can have your personal information like your address be removed from the public pilot database maintained by the FAA.
If you're concerned about the value of the radio, I'm not so sure an engraving mark would make it worth much less. People buy those things for utility, not necessarily aesthetics.