Workflow status property is correct. This setting can make the reporter field non editable while an issue is in the Completed status so a user with a role that otherwise allows changing the reporter still cannot edit it.

Workflow status property is applied to a status in the workflow and can mark specific fields as read only for that status. That behavior enforces field level restrictions based on the current status and it takes effect regardless of project level edit permissions.

Permission scheme is incorrect. Permission schemes control who can perform broad actions at the project level such as editing issues or changing the reporter and they do not enforce read only behavior only when an issue is in a particular status.

Field configuration is incorrect. Field configurations let you set fields as required hidden or optional for the project but they do not provide a way to make a field read only only while an issue is in a specific workflow status.

Issue security scheme is incorrect. Issue security schemes control visibility of issues for users and groups and they do not control whether a particular field is editable in a given status.

Workflow condition is incorrect. Conditions restrict who can execute a transition or whether a transition is available and they do not by themselves make a field read only for the duration of a status.

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