People ask for help in chats or on Reddit or go straight to Bugzilla which makes it more likely the same question is asked a lot of times.
A Help category could keep support requests in one place. Discourse can offer similar topics to check out before posting to avoid duplicates (is that set up?).
Troubleshooting - After a solution is found, the most common problems could be moved into a single thread with one answer outlying the chain of steps to try when having this problem yourself - maybe replacing Troubleshooting - KDE UserBase Wiki ?
FAQ - We could also create/move here the most common questions+answers (How to solve problem X in KDE Plasma?) so people will find Discuss sooner in search engines.
I feel that will separate out the debugging process from the solution. Often, while the exact solution doesn’t fit a user, the discussion on the issue thread helps them fix their issue. So I’d suggest having everything on Discourse itself and not separating out to separate page.
+1
If adding the auto lock thing, make sure that it doesn’t lock unsolved threads, or give a reasonably high timeout for unsolved thread to avoid necro bumping. Solved thread can be closed in 2-5 days of inactivity.
If you look at things like Stack Overflow’s success, it would seem that people don’t mind whether that solutions are in forum-like discussions, so my guess is that going to the trouble of transferring them to a wiki may be a low priority task.