Its a like a tick. Its often a boxers way of keeping themselves comfortable and an opposing trainers giftwrapped opportunity. Find something your charges opponent does consistently without fail and exploit it. Certain ticks are innocent enough. Like the one mentioned here. Its momentary and brings the fighters hands up to his face which wont often block his vision and fighters sometimes only dip into this behavior when their opponent isn't close enough to take advantage.

Others like Toe tapping on the back foot can leave you locked flat footed and off balance when someone rushes you; tapping your gloves together low or Adjusting the groin protector / trunks also pulls a fighters hands away from protecting his head. Glove twisting/hand rattling and my absolute pet peeve.. Drawing a hand back after landing a punch and posing with it half cocked.... can affect a fighters bio mechanics if hes caught wrong.