I had a follow-up exchange with the customer, and the feature request is actually more specific and is specific to the Discourse Assign and Discourse Solved (Accepted answer plugin) plugins. What they need is for the OP to be notified when there is activity related to these two plugins, e.g. it has been assigned/unassigned/reassigned and a reply has been selected as the solution. Just getting the emails about replies is not enough because there may be multiple replies until one reply is chosen as the solution.
2 Likes