I’m getting flashbacks to Stack ExchangOverflow, and various attempts to encourage people to accept answers on their questions… from memory, every attempt in that direction fell foul of the simple problem that nobody likes to be told what to do, and hit-and-run posters aren’t going to come back to see your admonition anyway.
There are settings to allow admins, mods, and various other high-value personages to tick “solved” on a post, and I think that’s about the best you’re going to be able to get.