In Preferences, users will eventually discover

• Add pages and files I edit to my watchlist

They will say that is a great idea, and enable it.
But then they will say "what about all those pages I edited
when it was unchecked? I wish Contributions had (solid)
stars next to pages that are in my watchlist, so I can tell
which of my Contributions aren't in my watchlist
already (and perhaps even click on empty stars right there
in Contributions to add them to my watchlist!)"