Per this Idea: Reminder system for helpful/correct answers, we have deployed the reminder system and are testing it out. For test purposes, it has been enabled here, in the Community Feedback (No Product Questions) space only. We are also testing this out in our behind-the-scenes moderator space.
The system should send reminder emails after seven days whenever a question is posted, the question has replies, and the user has not come back to mark anything Helpful/Correct. You should start to see these reminders for future posts; it is not retroactive to past posts. Here is the text of the email reminder:
Feedback is welcome on this new feature. We look forward to rolling it out globally!