I missed half the thread, and the intended subject, but the fact is it there is
no way in the world reversing the polarity of an AC plug can ever cause voltage
differential between two pieces of equipment. Nope, unless one or most likely
both are hot chassis and both have been tampered with in some way to compromise
the hot chassis safety features such as jumping caps etc. There's a minimum of
about 1meg resistance between hot chassis and any jacks, catv input ect. 1meg
sure isn't going to cause lights to dim or damage regardless of the polarity of
the cords.