Won’t that only work if the plates aren’t microwave safe?
I did smash an old plate once doing it on full power (would usually use 2/3rds!)
No idea if you’re supposed to (a quick google suggests maybe not!) but I’ve done it for years without issue. I have seen people suggest using damp plates or putting a cup/bowl of water on top.
It doesn’t work on mine, they must be a different sort of pottery.
I wouldn’t do it with your fancy gold leaf plates, no 🙂