I realize that when viewing a WorkItem, there is a "status" attribute. The problem is that some users just don't read it. There has long been an issue when users open a WorkItem via a link from an email, or have their WorkItem table view set to "Closed." They don't notice "Status: Completed," so they ask IT/Support why they can't do their work.
My idea proposal is broken into two complementing parts, which are certainly open to criticism and improvement.
1. When viewing the details page for a WorkItem that either a) has already been completed, or b) cannot be completed, first display a page telling the user that this is the case, that they are viewing legacy data, etc.
2. Create a Preference to manage (enable/disable) this behavior.