Would be nice.
I don't know why there should be a limit of 1; there's room on the c-rpg website for a 5000 character bio, surely storing the +3 names wouldn't be an issue.
I don't see what's wrong with the names appearing in-game - if you can't identify a longsword by its model, you have no business picking one up.
I imagine the owning a weapon with an obscene name would attract the same attention and the same penalty as owning a character with an obscene name.
Can't see any easy way to implement this in-game, as afaik, every player would need an identical item_kinds1.txt and updating that constantly could be a pain.
Agree that the names should be unalterable. Would also be cool if you could only do it if the item isn't traded between +0 and +3.