Iv heard of that possibly happening, but I torch the heck out of it, but I constantly keep the flame moving. It would certainty happen if you expose it to a radical temp change. Like when you boil water in a class container and add cold water to it. I did crack a ceramic when I forgot to take the rubber o-ring off the ceramic. It cracked the bottom right off of it.
After I torch it, I place it on a piece of thick metal so that it doesnt burn anything. I did one time place it on one of my cigar boxes and it scorched the wood.
Just use care when torching, it retains heat for a long time. Try to keep the flame moving so that you dont over heat it in any one spot to avoid cracking. If you take things slowly, and even do it a couple times, that would avoid overheating and cracking.