It's not quite the same situation as the mini plug. You are actually creating a ground loop each side of the contact point. Obviously the one on the chassis side is very short. Whether or not the other loop picks up hum has to do with proximity to EMI, and the shielding layout of the ICs themselves.
I've had it cause problems, and not cause problems. A small piece of electrical tape is recommended.
I've had it cause problems, and not cause problems. A small piece of electrical tape is recommended.