Arguably, the existence of Cell destroys any notion of immutability. It depends on your worldview; if an escape hatch of any kind makes immutability a lost caus

Arguably, the existence of Cell destroys any notion of immutability. It depends on your worldview; if an escape hatch of any kind makes immutability a lost cause, then this point has merit. But I don't see why that would be such a big deal, since the majority of the language is immutable by default.