I seriously cannot believe we are even discussing this...how is this not intuitively obvious? that weapon through one target, let's say you JUST happened to hit the exact point where a blade can pass through the elbow without touching bone, that's as good as it would get, agreed? Can you actually picture yourself then being able to, without actually intending to do so ahead of time (because you'd never be able to plan something like this), then keep that weapon going to inflict injury on another target that is standing nearby? This is not a lightsaber, it will not pass clean though things. You will have lost momentum. I think you can agree it's a pretty lucky thing for that to happen right?
Now I would argue that the likelihood of this actually happening is not nearly high enough to warrant letting every single penetrating blow in the game....let that sink in....pass through enemies like it was above mentioned lightsaber and continue to inflict damage. That is the system that is being discussed here. Not the occasional heavy two-hander blow to the arm that passes through, but every penetrating attack, even when made on a plate-armoured torso, as I understand it, will be able to do this.
This is insane.
I don't care what gameplay reasons you might have, but stop arguing it is even remotely realistic.