Super dangerous idea to add boiling - or even hot - liquid to carboy. Ever! The last thing you want to happen is a carboy to shatter in your hands. There have been many people over the years who have had serious laceration from breaking carboys. Serious loss of blood! It's probably a good idea to start reminding people of the dangers of glass carboys again.
Agreed! Prior to moving to stainless conicals, I was using plastic conicals for this very reason. Had an unfortunate meeting between the bottom of a carboy and a concrete floor a few years back, which resulted in a good gash on the bottom of my foot and the loss of a Corsendonk clone. Two lessons learned that day:
1) Never step foot in your brewing space with sandals, even if it's just to check the temperature of a fermenting batch. You'll likely end up messing around with something else, and it's best to be protected.
2) Increase your level of caution around anything glass in the brewing space -- even seemingly harmless pint glasses can cause some serious problems.