- Watch a page in mobile view and make sure the watch star is green.
- Edit it with the mobile visual editor.
- Save changes.
- Where the start was green (watched), now is white (unwatched).
I can reproduce this in mediawiki.org and my own personal wiki, with Firefox and Chrome.
In case it is useful, I lost the "watch" here: https://www.mediawiki.org/w/index.php?title=Translation_UX%2FDesign_feedback_1&type=revision&diff=2267891&oldid=1774991