It's always fascinating to read about people reverse engineering obscure tech like this. I don't even know where to start to acquire the skills to do something like this.
(Feynman said something to the effect that if one is always trying to solve puzzles, and always checking to see how other people solved them, then one day one will discover that one has solved something no one else already had.)
If the author had been as afraid as me of reverse biasing the circuit, he might not have gotten started. Try things, and if something breaks there's still something you can learn from that behavior.