How to opt out of curly-quote spamming altogether?

[Drew Adams <drew.adams@oracle.com>]

Could someone please remind me how to completely turn OFF the
aberrant and ubiquitous curly-quote virus?

(I have `electric-quote-mode' OFF, but that does not help with
existing doc etc.)

Even just to paste text from the manuals into an Emacs
StackExchange question or answer I now need to manually change
each pasted curly quote into a backtick, in order to get SE's
own code-inline highlighting (`...`).  (Previously I needed to
change only the apostrophe of `...' into a backtick.)

Naturally, I looked in NEWS for an option or mode, to turn this
OFF.  But naturally, NEWS is not yet fully written for this
"feature" (it likely will not be fully written until soon before
the release).

NEWS does mention, misleadingly, the "New minor mode
electric-quote-mode for quoting 'like this' and "like this"" -
as if turning that mode off would eliminate such quotation.
Presumably the final wording will make clear that, per the doc
string, this mode is only about "replacing [classic quoting]
with [curly-quoting] _as you type_".

There are at least 4 locations in NEWS where the new curly-quoting
is advertised, but I found nothing that tells me clearly how to
opt out of its spamming altogether.

I did find, buried in the NEWS entry "substitute-command-keys
now replaces quotes", mention of option `help-quote-translation',
whose doc string gives the impression that simply changing the
value will change the quote-style behavior: "Left and right quotes
are determined by new custom variable 'help-quote-translation'.
(This should not be only under a `substitute-command-keys' entry.)

But that is apparently not the case in general.  AFAICT, that
option has no effect on the quotation style used in the manuals.
They still show curly quotes, even though the option value is
now 96.  (As I said previously, the option values should not be
characters, which are shown to users as integers.  They should
be meaningful, easy to recognize strings or symbols.)

`help-quote-translation' does seem to prevent curly quotes in
*Help* buffers, so at least there's that.  But I'm looking for
a switch to turn this virus OFF everywhere - to return to
Classic Emacs.  Surely such a simple ON/OFF switch exists?
Perhaps info about it was buried in some of the voluminous
missives back and forth here, but a simple reminder would be
greatly appreciated.  Thank you.