On 4 May 2023, at 11:26, Timur Doumler via Std-Proposals <std-proposals@lists.isocpp.org> wrote:
Attributes are for ignorable things. I proposed to add an explicit Ignorability Rule to the standard – which we did for C++23:

Oops, forgot the link: http://eel.is/c++draft/dcl.attr#grammar-note-5 

Cheers,
Timur