Does anyone know a relatively simple way to move the rear sight without marring the sight or slide completely?
Padded vise ( I like to mask the sides of the slide with tape as well), Delrin punch, and an adequate hammer.
If that doesn't work try a brass punch (a little pencil lead on the sight will prevent the brass leaving marks). The punch tip can be filed/ground/machined for the best contact.
Still no joy: go to a bigger hammer.
The application of some heat seems to help get stubborn ones started. PB Blaster helps too.
A sight pusher is probably the best bet.
Delrin punch on a Kahr sight? Definitely skip to the brass, a thick diameter one.
If the sight really needs to be moved I would take it to a gunsmith. When I changed my sights on my PM9 I broke the front sights trying to take it off.
I think the only safe way to do this is if you have a sight pusher.