> Maybe, for Western languages, as the semantic equivalent of the
> presentational <big/> and <small/> elements. Those are being obsoleted
> in the XHTML 2.0 draft. So what's a semantic replacement for <small/>?
> 

Note that, for non-Western languages, small is used for positive 
emphasis in simplified Chinese.

I'm also not quite sure what the use case is for negative emphasis.
Most examples I've seen that could be called negative emphasis are
there to distract the viewer from important information that is
either boring or has negative conotations.

I think the developing trend is probably to style such things with
very low colour contrasts.