Far be it from me to promote bad habits, but some people just can’t help biting their fingernails. When I was a child, our nails would be painted with bitter aloes in order to force us to stop gnawing our paws…didn’t really work though.
Today’s invention is a way to allow the bad habit but preserve the underlying nails.
Edible, false fingernails could be bought and attached (briefly) to one’s own nails. These would be long and patterned and available in a wide variety of delicious flavours (including both sweet and savoury versions; maybe even sugar free and containing toothpaste).
Although absent-minded or nervous nibbling would still take place, at least this would not involve consumption of anyone’s bodyparts.
Before there’s a storm of protest from the food hygiene lobby, consider how free from germs the average teenager’s fingers are whilst they chew them. This approach would even allow a layer of nasty-tasting stuff to be incorporated within the false nails after the tasty bit was finished and the underlying, real nails were in danger of being bitten.