Bug: authors not notified when comment visibility changes from "Reviewers" to "Authors and Reviewers"

[robgjansen]

Sometimes reviewers write a comment with visibility set to "Reviewers", to solicit feedback on some questions they have for the authors. Later, a reviewer wants to send that comment to the authors, so they go back and edit that comment to change the visibility to "Authors and Reviewers" to make it visible to the authors too. When they do this, no email notification is being sent to the authors even though the interface does say that the authors will be notified. The reviewers are left waiting for a response to the posted questions, while the authors never realize a response is requested.

This issue was discover on v3.0.0. Just tested on 903edf1, and discovered that the bug still exists. See attached for reference.

I think the desired behavior is that when a comment is edited, if the visibility changes TO allow authors to view it FROM any type that does not allow authors to view it, we should send the author notification email.