WHY would it have been necessary for Carla to go through negative space/time?

[APeacefulWarrior]

Sounds to me, then, that there IS basically a safety-net in place. ie, it might be theoretically possible for a nuclear bomb to annihilate a spirit, but the deliberate activities of other positive entities will work to ensure this never actually happens. Which would just be the Creator self-adjusting to ensure nothing is ever lost despite our best attempts at doing incredibly unwise things.