Actually, the perfect afk weapon is the claymore, gladius, battle axe and bastard sword. If your character is rich enough, the anchets.
The kls is just a status symbol. A status symbol that is much much weaker then the anchets and claymore.. The only thing it is actually good for is to look cool. Even though it is smithed, the items used to smith it is only god (admin) given so it would be godly in power. As it is weak in power, as a status symbol (as in being gifted to a specific person by the gods), it is only reasonable that it would be unmuggable. As it is, it is one of the easiest things to mug. This is why you never see anyone actually carry them. They sit in storage. If they were made unmuggable, and someone wanted to use an "afk weapon", they would use one of the above mentioned weapons as they are more effective.