We recently had an employee leave the company. We moved the employee to “Viewer” status. Subsequently in some of our reports on Tasks by Person we found a weird “number” in the user field being reported on. We eventually figured out these were the tasks assigned to the user that left the company and who’s user type was demoted.
This is bad behavior for an application. There should be some placeholder that still identifies that user by name as assigned to the tasks (all were “done”) for historical purposes. Sure, they wouldn’t be able to be added to new tasks, but it should hold that user as part of the historical record of a project/board even if they are no longer a licensed user.