> If I use <samp>Hello World</samp>, I am quoting some output from a
> computer program. Same as <q>From where?</q> might be used to indicate a
> quote from a human. (Jukka in this case.)
> 
> Does XHTML need entirely different elements to indicate what type of
> entity is being quoted? Should we also have:

Yes, because there is already a precedent in conventional typography.
Conversations with humans are generally shown as peer conversations,
in quotation marks, even if one human is king and one is pauper.

Human to machine conversations are normally shown with different
type styles and with an assymetry between human and machine, probably
to avoid over-ampropomorhising (spell?) the conversation.