I appreciate the explanations. As I've mentioned once or twice before, I worked with an electrician who was super safe and super competent, but tended to answer my questions with, "Because I said so."
You can't fool a Wiggy with induced voltage, but be careful, they can play the devil with electronics. A lot of our wiring was done in the 1960's...no EGC and 480 and 120 in the same pipe.
Sometimes not getting what you want can be an incredible stroke of luck.
You are right. Maybe we should call them "reverse polarity testers". That is really the only difference between them and a night light ... unless there is a bootleg ground off that reverse polarity connected receptacle, then it says "OK".
McClary's: Welcome to ECN. The poster was referring to, in a disrespectful manner, the plug-in receptacle testers ... you know, the ones with three little lights.