Two notes on the "Cache-Control: no-transform":
- it is defined in the HTTP RFC. We advertise it in the guidelines
because it was neither well-known among content providers nor respected
by content transcoding proxies, but we do not alter its meaning. In
other words, an HTTP proxy should already respect this directive.
- I think we realize that it is a "heavy" switch, but we cannot invent a
switch that would better suit our purpose, e.g to narrow the scope of
the no-transform to "no desktop-to-mobile transcoding".
One way to address the comment could be to add a note to call out that
"Cache-Control: no-transform" is not limited to desktop-to-mobile
transcoding: it also prevents desktop-to-accessible,
mobile-to-accessible (and actually any type of transcoding), and should
therefore be used with great care.