List of steps to reproduce:
- Open a revision history page, e.g. that for w:Main Page, with Firefox.
- Click on a visible radio button.
- Use arrow keys to move the selection.
- The selection goes away. If you click "Compare selected revisions", it navigates to a diff showing the same revision on both panes (which says "No difference", of course) or a diff showing revisions in the wrong order (the newer one on the left and the older one on the right in LTR).
What should have happened instead?:
- Only visible buttons can be selected, and the arrow-key navigation loops once you hit a "dead end".