Hi Tom

Once a performance activity is closed then it can only be reopened through the manage activities interface. The manage activities permissions provides access to all performance activities that were created by the user so if this permission was allowed for the Appraisers they could open a whole performance activity or just the sections that need changing on request.

Using the save as draft could also be used so that the section is not marked as complete so wouldn't close so would be editable.

Another option is If you used the close on due date then the activity would remain open and editable until the due date is reached

regards