My teeth already keep them really short, actually shorter than is aesthetically advisable.
Nail polish is an interesting counter-incentive to putting my nails in my mouth, no so much for the taste, but for the toxicity. I may try that.
The thing about filing is not that your nails are too long. For some people the trigger for biting their nails is that they notice a piece of a nail sticking up far enough to be bitten. If they file the nails as short as they bite them, but completely even, then that trigger never happens, so they stop biting their nails.
Pretty much substitute filing for biting, because that looks nicer and is easier to modulate into something that does make sense.
Previous thread: http://lesswrong.com/lw/mnq/instrumental_rationality_questions_thread/
This thread is for asking the rationalist community for practical advice. It's inspired by the stupid questions series, but with an explicit focus on instrumental rationality.
Questions ranging from easy ("this is probably trivial for half the people on this site") to hard ("maybe someone here has a good answer, but probably not") are welcome. However, please stick to problems that you actually face or anticipate facing soon, not hypotheticals.
As with the stupid questions thread, don't be shy, everyone has holes in their knowledge, though the fewer and the smaller we can make them, the better, and please be respectful of other people's admitting ignorance and don't mock them for it, as they're doing a noble thing.
(See also the Boring Advice Repository)