DarkFather said:
I'm just saying this guy is hardened to pain and his reactions are weird and out of place.

I totally understand where you're coming from with your view, but to me, having been thinking about this for a bit now, I might compare it to something I know I've done many times. I'll bump my elbow on something or cut my finger and immediately say 'ow', even if it doesn't hurt whatsoever. It's just a natural reaction. Or it's like when people are at a baseball game and see a ball coming towards them. They are behind thick, strong netting, but they still flinch.

Could be viewed that way with Vader, I think. I mean, he wouldn't normally have any reason to react in such a way in day to day life. It's not like stormtroopers whack him with sticks when he walks down the hallways.