In fact, since Spike's arc in Buffy really was complete, I'd say further story about *him* would likely be upsetting. It's just that I think to understand *her* story we need a clearer picture of how she thinks things ended with Spike.

Yes! Exactly. I don't need for Spike to come back to continue his story. I need for Buffy to stop being in the dark - I want to understand her. Does she know Spike is alive? How does she feel? That's what I care about the most. I don't need them to get back together, I just want some acknowledgment of the huge story that came before.