A sluffer (from the root word slough) is someone who does not take a valid hit on the field during combat. The penalties for sluffing are warnings, removal from battle, day suspension, month suspension, three month suspension, six month suspension, year suspension, and permanent ban. These are the legal, Wandering Ronin rule-book approved methods of dealing with sluffers.
Individual players will react differently to sluffers:
Some will be nice and ask politely in case the shot was simply not noticed in the heat of battle.
Some will call attention to it by informing their officers to watch for the behavior.
Some will stirve to make cleaner shots that leave no doubt the sluffer was hit.
A few will strike a sluffer harder to make sure the shot is felt.
A few will strike for strike-legal sensitive regions of the body, looking to evoke a pain response that removes doubt about the hit.
All of these methods ARE legal, even if some are of questionable intent.
It is NOT legal to make an illegal weapon to strike a sluffer with, intending to cause serious pain and physical damage. Possessing such a weapon with this intent is grounds for an immediate ban. Work your way down the list above if you encounter a sluffer: never use a weapon designed to cause harm.