Thanks Jake for the background and history of this.
I guess when I saw this new/old feature I thought it was a step towards implementing note taking. That is a very nice feature that is lacking in Moodle. I know there are other plugins but having notes unified with messages and other person-centric stuff in that side panel is highly desirable and from a usability standpoint would help clean up some things.
If the intent was to just re-implement something that was lost this seems to do the job.
The issue we have is that once the starred message is deleted the user is lost when it comes to taking a personal note. It is now a secret that no one would know how to get back. Then the issue is how valuable of a feature is it to invest time and effort to create an account on Moodle.org for a student to ask a question (if they even know to do this). At this point the user will give up and move on and never take notes again.
There is nothing to indicate you can take notes by messaging yourself from the user interface. That is knowledge that the teacher or another user must know in order to regain note taking capabilities. There are no instructions or anything within the moodle interface that would point a user to take a note once the original is removed.
I've used Moodle for over a decade and this note taking hack was news to me! If you were looking for feedback this is my two cents.