If I go to a page such as
https://en.wikipedia.org/wiki/Special:WhatLinksHere/Example
and click on watch I always get
"An error occurred while changing your watchlist settings for "[[Special:WhatLinksHere/Example]]"."
I don't remember seing this on MW 1.18.
Version: 1.19
Severity: normal
URL: https://en.wikipedia.org/wiki/Special:WhatLinksHere/Example