Eli Zaretskii <eliz@gnu.org> schrieb am Mi., 30. Nov. 2016 um 17:25 Uhr:

> > From: Lars Ingebrigtsen <larsi@gnus.org>
> > Cc: Eli Zaretskii <eliz@gnu.org>,  p.stephani2@gmail.com,
> kentaro.nakazawa@nifty.com,  emacs-devel@gnu.org
> > Date: Wed, 30 Nov 2016 16:48:09 +0100
> >
> > Yes, this is not a json.el problem at all.  It does the correct thing,
> > and shouldn't be changed.
>
> ??? Why should any code care whether a pure-ASCII string is marked as
> unibyte or as multibyte?  Both are "correct".
>

I guess the problem is that process-send-string cares. If it didn't, we
wouldn't have the problem.
For URL, we'd need functions like
  (byte-array-length s) = (length (string-to-unibyte s))
  (process-send-bytes s) = (process-send-string (string-to-unibyte s))
(conceptually; process-send-string also does EOL conversion, which should
never be done for HTTP bodies.)