When we do reviews, the author of the change generally comments on every place that changes have been made, then the reviewers discuss them (at the very least, saying "yes, this looks good".) This generates a lot of chatter, and an equal number of e-mails—a number so great, that it caused many of our team members to disable all e-mails from Kiln and FogBugz! Obviously, that's not a desirable outcome: we want people to be able to receive notifications.
We currently use another tool, Code Collaborator, for doing code reviews. Code Collaborator's e-mail notification feature has an option to limit the number of e-mails you receive, and it works similar to Mediawiki's "watch this page" feature. If a review changes (eg, someone makes a comment,) you receive an e-mail with that information. Then, until you visit the review, you receive no more e-mails that day. Only after 24 hours have passed with no visit to the review is a reminder e-mail sent with updates to the review since the last e-mail. This limits the flood of e-mails that you can get to at most 1 per visit per review.
I'd love it if this notification method could become an option (or perhaps, the default, since we always had our CC users switch to it!) in Kiln.