While my gelding was in training he had his whiskers clipped. Partially because my trainer is a show trainer and that's what they do, and because we were working on getting him used to clippers and needed something to clip! He was stalled with daily turnout while he was there and didn't have much time for mischief, so it really didn't matter. He didn't seem to care.
I don't do it because I am lazy and he is a pasture kept trail pony in training. No reason to.
Proud owner of ~Mana: 6yo Arabian gelding~Pearl 13yo Arabian~Danzer 14yo Arabian mare~ Tiny mini filly