When changing setting in issue tracker to "Unassigned," it is shown as a change to "Anonymous"

The "Issue settings" in the tracker include an "Assigned:" setting. By default, that setting is "Unassigned" until someone puts his or her self forward, when it is changed to "[Individual'sUsername]". But sometimes it's necessary to change it back from the individual's username to "Unassigned." The problem is that, though the change to "Unassigned" goes through correctly, it appears in a post as "Assigned to: [Individual'sUsername] >> Anonymous." This is very confusing for some people who aren't interested in being anonymous. It happens all the time, but an example of the problem in action is #70911: F10 and F11 without result. It should be, instead, "Assigned: [Individual'sUsername' >> Unassigned."