"_____'s Spirit is Fading Away" Message. What is this?

Interesting. I haven't seen anything like this in my game. My guess would be they're giving you a chance to save the ghostly version of a Sim, prior to culling. If that's the case, I think it's a great thing to implement. Gives the player a bit more power over what's happening in their game. I will bookmark this thread, as I am quite curious, too, to learn the answer.