I don't understand. The lead discusses this page as an on-going proposal. Yet there is an "Outcome" section. So what is the status of this page? Are new proposals still accepted?
Topic on Talk:New requirements for user signatures
The validator in Special:Preferences was implemented, but it was determined that it was not necessary at this time to require that existing signatures be changed. I am not aware of any ongoing work in this area, nor any intentions to do any work in this area.
The proposal is accepted and closed, but the project to implement it is still on-going, or at least not finished. New requirements for user signatures#Outcome says that non-conforming signatures will be disabled, but this was not done yet (T248632), except in two projects where local community volunteers led that work (T355462, T364769). See also current state of the relevant config here.
The page could probably be cleaned up a bit, it stayed in limbo after the Editing team has moved on to other work.
If you wanted to propose more signature requirements, I suppose you'd do that in a Phabricator task instead.