I have updated 2558R1 with the requested addition of Annex C to Wording.
https://isocpp.org/files/papers/P2558R1.html

Add to Annex C

*C.n C++ and ISO C++ 2023* [diff.cpp23]

*C.n.1 [lex]: lexical conventions* [diff.cpp23.lex]

1

*Affected subclause:* [lex.charset]

*Change:* The characters $, @, and ` may not be represented as a
*universal-character-name* outside a literal

*Rationale:* Inclusion of these characters in the basic character set.

*Effect on original feature:* The characters were not allowed in
semantically meaningful text outside of literals, but could still be
present in early phases of translation as *universal-character-names*.

[Example 1:

 <https://isocpp.org/files/papers/P2558R1.html#cb2-1>#include
<stdio.h> <https://isocpp.org/files/papers/P2558R1.html#cb2-2>
<https://isocpp.org/files/papers/P2558R1.html#cb2-3>#define STR(x) #x
<https://isocpp.org/files/papers/P2558R1.html#cb2-4>
<https://isocpp.org/files/papers/P2558R1.html#cb2-5>int main()
<https://isocpp.org/files/papers/P2558R1.html#cb2-6>{
<https://isocpp.org/files/papers/P2558R1.html#cb2-7> printf("%s",
STR(\u0024)); // Was allowed, now is not an allowed UCN
<https://isocpp.org/files/papers/P2558R1.html#cb2-8>}

— end example]

[Example 2:

 <https://isocpp.org/files/papers/P2558R1.html#cb3-1>#include
<stdio.h> <https://isocpp.org/files/papers/P2558R1.html#cb3-2>
<https://isocpp.org/files/papers/P2558R1.html#cb3-3>#define EAT(x)
<https://isocpp.org/files/papers/P2558R1.html#cb3-4>
<https://isocpp.org/files/papers/P2558R1.html#cb3-5>int main()
<https://isocpp.org/files/papers/P2558R1.html#cb3-6>{
<https://isocpp.org/files/papers/P2558R1.html#cb3-7> EAT(\u0024) //
Was allowed, now is not an allowed UCN
<https://isocpp.org/files/papers/P2558R1.html#cb3-8>}

— end example]


On Mon, May 9, 2022 at 5:30 PM Tom Honermann via SG16 <sg16_at_[hidden]>
wrote:

> SG16 will hold a telecon on Wednesday, May 11th, at 19:30 UTC (timezone
> conversion
> <https://www.timeanddate.com/worldclock/converter.html?iso=20220511T193000&p1=1440&p2=tz_pdt&p3=tz_mdt&p4=tz_cdt&p5=tz_edt&p6=tz_cest>
> ).
>
> The agenda is:
>
> - D2286R8: Formatting Ranges
> <https://brevzin.github.io/cpp_proposals/2286_fmt_ranges/p2286r8.html>
> - Review and approve final wording updates.
> - D2558R1: Add @, $, and ` to the basic character set
> <https://isocpp.org/files/papers/D2558R1.html>
> - Continue review pending the availability of an updated revision.
> - D2572R0: std::format() fill character allowances
> <https://rawgit.com/tahonermann/std-proposals/master/d2572r0.html>
> - Continue review pending the availability of an updated revision.
>
> I expect this to be our last review of P2286 unless something surprising
> and new is identified.
>
> Further review of P2558 and P2572 are still contingent upon new draft
> revisions by their authors. If new revisions don't materialize, then we can
> hope for quite a short meeting!
>
> Tom.
> --
> SG16 mailing list
> SG16_at_[hidden]
> https://lists.isocpp.org/mailman/listinfo.cgi/sg16
>