There are many places in core where a link with the "button" role is used (a[role=button]). The expected behavior of such an element is that it responds to the spacebar (and obviously to the enter key and to click). For now, most of the time, it does not respond to the spacebar, which is an accessibility problem.
It's easy to add some JS code to give all "pseudo-buttons" the intended behavior. But we want to make sure this won't break anything.
The first thing to do might be to detect where it's used in core, and where adding the correct behavior could break the UI.
This is a follow-up of . We had a discussion with andrewmacpherson at DrupalCon Dublin about this. We thought it would be nice to open this wider issue. Screenreaders tell the users that
<a role='button'> is a button, so the users expect the spacebar to respond.