FYI that comment is full of inaccuracies.

Molecules moving doesn't cause friction, which creates heat and increases temperature . The vibration of molecules IS temperature.

Heat transfer also only works from the hotter object to the colder one. Once the plate is hotter than the food, heat transfer can't possibly be occuring from the food to the plate. It's the other way around.

So the reason the plate is so hot can't possibly be that it's taking heat directly from the food. The plate's material is absorbing the microwaves.

That last paragraph doesn't even make sense.