Below the arrows for up- and downvoting questions we have the star to make questions favorites and see how many users did so. When I didn't click the star but somebody else did, the tooltip reads:
This is a favorite question. (Click again to undo)
This seems misleading since clicking it won't undo anything, it will make it a favorite question for me as well.
The tooltip even says the same when nobody chose to make it a favorite question. In this case 'This is a favorite question.' is just wrong.