How do you unstar a level in Super Mario Maker?
There seems to be no way to unstar a level.
Some anecdotal experiences: 1, 2
There is, however, a way to comment without starring a stage.
- Play (and possibly clear?) the course
- Go to Course World
- Press -
- Select Played Courses
- Select View Comments on the course you want Comment in the Miiverse area.
Source