I've never heard of a procedure to make someone shorter, but I've heard of people who try to get their legs stretched to make themselves taller, and it's supposed to be painful and dangerous, as you can imagine. I read on the web that people who get their legs stretched sometimes become taller, but they aren't able to walk! I expect an operation to make one shorter would have similar problems! It would be hard to be very tall - always too tall to easily look someone in the eye, for example. One might feel awfully conspicuous and out of place. I wish your friend luck in accepting his height.