It's an interesting complaint. Yes, Buffy has the option of feeling sorry for him if she wants to. IMO, she doesn't show much sign of that, exactly. It's more like she takes him/his situation a bit more seriously, not so much that she pities him. IDK.

But if people want evidence that a soul makes a difference, what other sign of that would they like to see? If he came back the exact same, then wouldn't that mean that the soul is without importance? Which, again, is an interesting possibility, but not the one we've got to work with.

Thanks for a post that inspires the thinky thoughts!