The Discourse meta forum https://meta.discourse.org/ has a plugin that allows to mark posts as “solved” when a questions has been answered, also highlighting the post that contains the solution:
I think this would be a good addition for the 
forum too.
many users asked on the old forum how to mark the topic as solved, this could be valuable…
Agree. Would be great addition. Won’t be used by everyone though. I had similar thing at one of the forums I’ve maintained for years. It was used in ~40% of cases.
It was used in ~40% of cases.
still good. also moderators may mark correct answers, does not necessarily be done by the people asking.