A brief update:
I'm happy to announce that most of the educational notes infrastructure has now landed on master, and the feature is now enabled by default! As a result, the hidden frontend flag enable-educational-notes has been removed. Notes can be shown on the command line by passing the new -print-educational-notes flag.
I've also created a jira task to track expanding coverage to more diagnostics, and added a quick-start guide which assumes no prior knowledge or contributions if anyone is interested in adding their own.