Some CLF people can do this- had it happen to me just as a kind of demo by a CLF master.
" If I don't want to hurt someone I will sting him- pinch him- don't have to hit him- If I hit him, it will hurt him pretty bad"
I tried to punch him for real he told me too- he got to my biceps and triceps, kind of a half circle grab, the biceps hurt more on the triceps. Yeah no I did not want to holler but;
yeoooooooooohhhhh! damn dat hurt! some kind of a tiger claw type hand formation- next day small patch of skin off of the biceps size of a small nail head, the triceps-- golf ball sized bruise with a patch of skin missing in the center the size of a pencil eraser. I tell you this would change your mind quickly if it happened in a confrontation, and I think this was just a small taste of it....
I was told he pulled a patch of skin off of the inside of the thigh of a large karate guy who tried to round kick him- in front of the karate guys student's... I am sure that was no fun at all.