> I am operating on the assumption that we had better be prepared for the
> CSS not being applied as we intended (someone may swap in a different one
> for audio rendering, for example), so preserving the basic div/span
> distinction in HTML seems pretty important to me. I may well be wrong-
> headed there.
I think it's a reasonable assumption (the css not always being applied). E.g. a web archive environment might leave it out, or a tool for text analysis.