I have seen a lot of instructors with these, and was of the opinion that it was the domain of the guards, and not other units. Then I met the provo sergeant from our regular battalion, funnily enough with a slashed peak, but I seem to remember being told by an instructor when I was a cadet that it was a bad thing to do, as you could get in trouble for defacing uniform. Is there a definitive answer? Is it walting by these self appointed "drill pigs"? Your answers would be a great help to me.