Paul Eggert <eggert@cs.ucla.edu> schrieb am So., 31. Dez. 2017 um 00:07 Uhr:
Philipp Stephani wrote:
> As discussed in
> http://lists.gnu.org/archive/html/emacs-devel/2017-10/msg00051.html, we
> (mostly) agreed to first turn them into errors

And we've done that in Emacs 26, right?

No, only in master (i.e. Emacs 27), see http://lists.gnu.org/archive/html/emacs-devel/2017-10/msg00056.html
 
So in Emacs 27 we can remove support for
old-style backquotes;

Only in Emacs 28, because 26 will still have old-style backquotes only.
 
we don't need a new variable to enable old-style
backquotes dynamically.

My patch conditionally enables new-style backquotes; there's no way to re-enable old-style backquotes once they generate errors. The assumption is that everyone should migrate to new-style once they get the errors, and not re-enable old-style.