If I am looking at the page for a ArcGIS Online hosted Feature Layer it has a 'Share' button my understanding is that this allows sharing with View Only privileges. If I want to add editing privileges, I need to go to Content and check the layer and use the 'Share' button there.
There should not be two layer modification buttons both labeled 'Share'
Perhaps one should be 'Share View' and the other 'Share Edit'
It would be nice if sharing editing capabilities could be accessed from the layer page. Typically anything about the layer should be able to be viewed or changed from the layer page itself.