@stjn: Is this about MediaWiki core? Asking as there is no codebase project tag associated to this task.

Yes (is it MediaWiki-General that I should’ve put?).

Seems like something of an interest for Codex efforts as well, since it could provide an increased use of accessibility text in the projects, which is a net benefit for UI standardisation.

An established practice to make content visually hidden, screen reader-visible seems to be using CSS like this

.sr-only {
  border: 0; 
  clip: rect(0 0 0 0); 
  height: 1px; 
  margin: -1px;
  overflow: hidden;
  padding: 0;
  position: absolute;
  width: 1px;
}

A simple example where it can be used:

In the style guide for copy, we see this:

The text "Warning!" is redundant for regular users – there is already a yellow box and an icon. But users of screen readers should see it (role="alert" is not quite relevant here, and I'm not sure if aria-live="polite", which OOUI messages use, is).

@stijn Thanks, you're right. I've misunderstood just based on the last comments.

Removing three non-related work areas though.