He'd had the right hand for more than half his life now, and the rest only barely less than half now. They are him. Flesh or metal, it didn't matter, he'd melded them to himself.

Vader had been tormented by phantom pains since he was a teenager - and it said much about the twisted nature of the Dark Side that he'd inflict that own kind of permanent pain on his own son, whom he admitted to loving, who he attempted to protect and strengthen. However much guilt Vader felt about that, even if here it wasn't done, it just added to his own personal torment.

"In the Force? Yes. With my right hand as clearly as you would with yours. The other limbs are more muted in sensation. Sensation passed that is different. Scar does not transmit as normal skin. Pressure and pain most clearly, old scars feel heat, cold, touch the least. Fresh ones feel them more, unless they are just layering the old, as those nerves are long since gone. Mustafar's lava bank took those long ago." Which had been a trick, he'd been sure, back then. The worst of the burns hadn't hurt. He'd been cold, without skin he'd been unable to hold his own body temperature, and it was still something he constantly fought to do. Without the Force it was impossible.