im a dom and thought id say a lil. i enjoy seeing leaving welts and scratches on my porclain skinned sub and he does tend to bruise easily (one time we were at a store and i pinched his but and he just smiled at me then later found i gave him a nasty bruise and it was thru jeans!) but i know ways to prevent horrible bruises.
1. take no blood thinners like asprin before a beating.
2. warm the skin up first.
3. if appendages are bound, i dont beat them hard!
bound breasts are easily damageable and easy to cause permanent damage. also, a bruise that shows up immediately isnt as bad as one that takes 3days to appear. because ones that take a few days means deeper tissue was damaged and it has taken that long to surface. but boobies are sensitive as it is + dont have muscle beneath like a booty. the capilaries are easier to bust and tho it does look very sexy just the rope can leave blood bruises..
if he was squeezing them so hard they bruised do the same to his dick and c the reaction. a grimmace of pain, a flash of anger and a moment of pleasure. . . though very different equipment the same emotions r attatched.

all in all I personally talk to him first whenever I'm n a mood to play rough. something i wish more people knew how to do especially when trying to earn trust in a relationship.