I see the feature in the Lithium Forums software: it send a letter to a question’s author in a week after the question to engage him to choose a solution:
Your topic recently received a reply.
Topic: …
Date: …
Did it solve your problem?
Click here to view the reply and mark one as an Accepted Solution.
This helps others find helpful answers in the community too!
As I just said here, it might be very effective:
https://meta.discourse.org/t/discourse-solved-accepted-answer-plugin/30155/117?u=alefattorini
Any thoughts about it? Just looking through the support category, I can notice that just 20 topics of 100 are checked as resolved. Is it a real stat? Or it’s only that OP doesn’t remind to check topic as solved?
I don’t know, I view the “accepted answer” as a “nice to have” as opposed to a “every loop in the system must be closed”
Bugging people with email is a two edged sword, it may be effective, it may cause them to devalue emails from Discourse.
Yes, but simply people don’t remind to check or answer and confirm the solution. Often I have to mention them requesting their attention 
This is also a huge problem for us. If people aren’t accustomed to participating in Q&A communities like SO, for example, it doesn’t occur naturally to them that there’s any value in marking a reply as the Accepted Answer.
We could reply to the topic but that would only unnecessarily bump it. We could send a private message but that’s harder to track and people other than the poster won’t get any education that they too should accept answers.
Currenlty I MUST re-read the entire support topic checking the right answer and using admin’s powers!
How about a Forum reminder instead (without an email)?
