review remarks

content/en/docs/concepts/workloads/controllers/job.md

@@ -1010,6 +1010,12 @@ status:
 
 {{< feature-state for_k8s_version="v1.30" state="alpha" >}}
 
+{{< note >}}
+You can only set `ManagedBy` field on Jobs if you enable the `JobManagedBy`
+[feature gate](/docs/reference/command-line-tools-reference/feature-gates/)
+(disabled by default).
+{{< /note >}}
+
 This feature allows you to disable the built-in Job controller, for a specific
 Job, and delegate reconciliation of the Job to an external controller.
 
@@ -1023,10 +1029,27 @@ installed, otherwise the Job may not be reconciled at all.
 {{< /note >}}
 
 {{< note >}}
-When developing an external Job controller make sure it does not use the
+When developing an external Job controller be aware that your controller needs
+to operate in a fashion conformant with the definitions of the API spec and
+status fields of the Job object.
+
+Please review these in detail the [Job API](/docs/reference/kubernetes-api/workload-resources/job-v1/).
+We also recommend you running the e2e conformance tests for the Job object to
+verify your implementation.
+
+Finally, when developing an external Job controller make sure it does not use the
 `batch.kubernetes.io/job-tracking` finalizer, reserved for the built-in controller.
 {{< /note >}}
 
+{{< warning >}}
+If you are considering to disable the `JobManagedBy` feature gate, or to
+downgrade the cluster to a version without the feature gate enabled, inspect
+there are no jobs with a custom value of the `spec.managedBy` field. If there
+are such jobs, there is a risk that they might be reconciled by two controllers
+after the operation: the built-in Job controller and the external controller
+indicated by the field value.
+{{< /warning >}}
+
 ## Alternatives
 
 ### Bare Pods