Did I understand correctly that mentions and tags are the same thing?
Then wouldn't
Code:
<mention>fly</mention> guy
and
Code:
<mention>fly guy</mention>
achieve the distinction? (Except replacing the angled brackets with square brackets. It seems even the CODE tag doesn't "escape" square brackets)
EDIT: something I saw while previewing this post makes me thinks semi-colons might work too? e.g.
vs.