The newly added opt-out link in the sidebar (T243281) is currently missing a title attribute. Title attributes allow people (and possibly screen readers?) to learn more about a link when hovering over it.
Suggested text: Change your settings to go back to the old look of the skin (legacy Vector)"
- Visit https://en.wikipedia.beta.wmflabs.org/wiki/Main_Page?useskinversion=2 while logged in.
- Hover cursor over "Switch to old look" link in sidebar
- Verify that tooltip appears with text that says "Change your settings to go back to the old look of the skin (legacy Vector)"
QA Results - Beta