If its a well-made rifle and the builder XXXX is known and regarded, the dedication to the owner generally doesn't bother me and doesn't affect how much I would value the rifle. I have a couple guns in my collection that have a prior owner's name on them. I hope that person would have been happy to know I enjoy the gun as much as they did. I actually think its a shame when these things leave the family, and hopefully you will have a relative that will remember that one as your gun.
Over the top excessive writing and carving, or a faux statement that proclaims the gun to be something it's obviously not (like Davey Crocket's gun) I don't particularly care for.
Unknown builder, a gun with sort of average quality or components, the dedication would be a detractor.