I started down this path because I have a no-name LED set with 50 lights and they all checked good with legacy light tester. Filament light tester will drive the LED bulbs if inserted correctly (trial and error, but they are keyed to go in socket only one way) What the legacy tester will not do is find the break in the 115 VAC on the line because it is passed to the repeater socket. Also the clicky piezo pop-voltage function should not be used because it is designed to activate the shunt in legacy filament bulbs, not LED bulbs.
So I still don't know how my sting is wired or why the voltage seems to be passed down the string but the LEDs aren't getting the required forward voltage.
It does sound like alot of folks have miswiring on their house outlets and should just buy one of those testers that shows their hot-neutral and ground are properly connected. On that note, my string uses two 3 amp fuses in the plug which both test less than one ohm and there are three wires connected to the spades which are not keyed for hot and neutral. As in the plug can be inserted either way. Best advise I got from this web page was go buy another string and keep these bulbs for spares.