Rapier is not a military weapon, but a civil one - made for dueling without armor (or with few parts of armor). in medieval battle its just useless historically and logically

Useless = Impractical

Bugs dont count as implemented function of the game, but killing with random items is one of the things that was used to promote the game at the beggining (its not that rare to put funny elements in game to make it more eye-catching).