I think it is sensible to require encoding of all the characters that
Windows doesn't allow in path components, viz.  #\<, #\>, #\:, #\|,
#\?, #\*, and #x0; through #x1F;.  Posix allows all but #\x0;, but
the remainder, though technically permitted, are nothing but nuisances
in pathname components, as they must be escaped when referred to from
the shell.  (#\: is an exception, but doesn't show up in Posix filenames
often either.)

In addition, the Windows executive treats #\\ and #\/ both as path
separators, a fact occasionally convenient, although the UI disallows #\/.
So I'd escape both of them in all cases too.

--
Work hard,                                      John Cowan
play hard,                                      xxxxxx@ccil.org
die young,                                      http://www.ccil.org/~cowan
rot quickly.