I don't think it's possible to move posts between users.
UNSOLVED Solved / Unsolved badge
How to add the Solved/Unsolved badge to NodeBB topics?
Hello @H7 -- you'll want to use the Q&A plugin: https://github.com/NodeBB/nodebb-plugin-question-and-answer
You can find it in the Plugins menu, or if not, then you can likely install it via npm.
@julian Thank you!