if you sit there with the key in the ignition on position, the coils will fry. it wont be instantaneous but they will start to heat up and melt.
yes you dont have to sit there with the ignition on, but since he already has the turbo module, then why not...
if you loan the car to someone or if it is at a shop (getting tint, mechanic, etc..) , they may leave the ignition on.
I like keeping the car as daily drivable and "stock" as possible. Having to worry about not keeping the ignition on for a period of time is not something i want to do.
i know they'll fry if you sit there. but i never just sit somewhere with my key to the on position. the only time i let anyone touch my car was for inspection but i made sure my friend who worked at the Merchants knew about it.