Hot-editing updates behavior while keeping state, causing wildly unpredictable behavior given the way objects are constructed from classes in today's languages. The current approach to OO is to bootstrap fresh state from an external source every time the behavior changes so guarantees can be made about the interaction between behavior and state. It seems to me the equivalent of using a wheelchair because you might stumble while walking, the concern is genuine, but the cure is possibly worse than the affliction.

I don't know what the solution is. Perhaps a language with a fundamentally different view of objects, maybe as an ancestry of deltas of state/behavior pairings, somewhat like prototypes but inheriting by versioning and incrementally changing so that state and behavior always match up but still allowing you to revert to a working version. Likely Alan has some better ideas on what sort of language we need.