Joseph-
You are right as far as the meaning of the word microtonal to the
punk on the street. However, to the average guitar musician, the term
"alternate tuning" means something like DADF#AD.
John Starrett
http://www-math.cudenver.edu/~jstarret/microtone.html
Linguistical extrapolation might lead one to count semi-tones as microtones,
too.
'Microtonal' seems like a suitable description (or even class) for otherwise
normal instruments such as refretted guitars or new keyboards, regardless of
the intervals that actually are executed with them by a player.
Clark