When publishing services to ArcGIS server you have the option to either allow or disallow geometry updates.
This is very useful when the service is used in collector to prevent accidental movement of geometry.
Unfortunately this appears not to be available for data that is hosted in ArcGIS Online. The only options you have when publishing to AGOL is create, delete, query, sync and update.
Will the Allow geometry updates option be coming to AGOL hosted feature services?
