If you have a datafeed configured, your users will have a "Managed By" section on their profile in edit mode. This has one of two modes it will display. The first is Managed By Manually, meaning that the user was created manually, and can only manually edited. The second is Managed By Some Datafeed Name. This shows that the user was created, and can only be edited via the named datafeed.
Note that you cannot edit users who are managed by a datafeed.