As a contrived example, is it fine to plug a Thinkpad USB-C charger into a MacBook power supply? Or perhaps a random 5V USB-C charger with a 20V one (yes I am familiar with diodes)? It doesn't make sense obviously, but the plug fits and someone, somewhere with particularly bad cable management will do this. Does the USB-C standard ensure that sparks will never fly or is this responsibility of the end user?