Eh, no more damaging than being KO'd from any other strike really. Either way, brain damage sandwich.makes for great excitement, but is very damaging for the fighters.
still, if they were legal, tactics for making the most of the rule would develop. mma would become: grappling to achieve dominant position on the floor before inevitably standing up to throw kicks. that would be awesome to see, but asks too much.
One of the nastiest KOs you'll see for a while.
Knocked sliding on his ass. Spun on his back.
Beautiful but VICIOUS!