What version are you running?
2.0.20
What's the URL of the page this enhancement relates to, if any?
N/A
Describe the enhancement and the motivation for it.
When publishing an edit to a review request, if the only thing that changed was the addition of new reviewers, could Review Board email only those people instead of emailing all reviewers?  I wouldn't expect existing reviewers to care about being notified when other reviewers are added, and this would reduce some of the email that Review Board generates.
What operating system are you using? What browser?
N/A
Please provide any additional information below.