It is not actually a bug (because it works), but I just wish to draw your attention. In Weapon* classes such functions as LineAttack and AimLineAttack in some cases are called from Owner variable and in other - from Player.MO. (And sometimes from 'pmo' which is a local variable, equal to Player.MO.)

Owner is also a local variable pointing to Player.MO, it's used like a shortcut. So basicly it's the same thing.