I have a post-function to add a public comment and fire an issue-commented event so that JSD will send an email notification. The comment is added as expected, but no email is actually sent.
Using ScriptRunner, I can see that the event does not have an sd.public.comment property. I suspect that the JSD notification listener is looking for that property and opts to do nothing if it's null. (However, the sd.public.comment property for that event is still being recorded in the entity_property table.)