This bug might not be very fixable. But here's what I did.
I created a new review request and added someone to it. Then, I went to
look at the diff to make sure it was okay. At that point, I thought better
of including that person on the review, so I hit the Back button. The
reviewer was gone.
Since the review request creator always shows a 'save' button every time
you make a change in the review metadata, I assumed that the change had
simply been lost because I didn't hit save. I added my group to the review
instead and then hit save, then publish. The ghost reviewer was back!
I don't know what a good plan of action for this bug is, but it's
definitely a usability nit.
