With CONSOLE-2202 the user is going to get a warning message when he tries to directly edit a resource managed by an operator (that is going to revert the changes).
The open issue is that the existing feature checks only the ownerReference but, as for https://kubernetes.io/docs/concepts/workloads/controllers/garbage-collection/ ,

Cross-namespace owner references are disallowed by design so an operator running in a namespace cannot set, by design an ownerReference on an object on a different namespace or on a cluster wide created object.

Proposals:

• custom annotation
• k8s recommended labels - https://kubernetes.io/docs/concepts/overview/working-with-objects/common-labels/