A good "if" ... related:  "if" the document is directly created or
consumed by humans, we should use some locale tagging.  ("xml:lang"
identifies language, not locale!)
> It looks attractive at first sight, but think of the burden you're
> placing on processors ... readers now
> need to know (enough about) *all* the locales from which they might
> receive data.
I'd contend that the "float" (or "r4") data _type_ doesn't have any
such localization issues.  IEEE floating point is a binary spec, and
nobody's proposed not assuming IEEE floating point.
Rather, this issue is an encoding issue.  By and large, having just
one (canonical) form is a lot easier for programs to deal with:  smaller
code, easier to debug, faster in normal cases, and so on.
But:  is this data being generated by/for programs, or people?  People
have different priorities than programs.
- Dave