I've been shocked using plastic pliers also. Maybe it's just the universe taking advantage of the opportunity to mess with me. I've been shocked so damn many times it's not even funny anymore.

Well, I should say it's not funny to me. There's no end to the amusement I generate for spectators.

I can't see what suggestion was posted but I often use short lengths of vacuum tubing between plug wire and coil then use a test light from ground to the vacuum hose. I am also likely to use a grounded test light at the end of the spark plug boot if I choose to disconnect the plug wire while the engine is running.