**Steps to reproduce:**
# Create a terrible, bug-ridden revision with some set of reviewers.
# Realise the error of your ways and run `arc diff --update` on //$#*!//:
## Apologise profusely and hope you don't get fired.
## But, then a shiny object appears, and you get distracted before exiting your editor.
# Alice, not a current reviewer, approves the diff. This adds them as a reviewer.
# Suspecting that shiny object was actually Dave playing with a laser pointer, return to your desk and `:wq` out of Notepad™
**What should happen:**
You regain your honour by fixing your code.
**What happens:**
Alice is removed from the diff