As of this post, registered users should all have the ability to mark threads that
they have created as "solved", which prefixes a [SOLVED] tag to the front of the title as well as closes the thread.
It's been a recurring suggestion that has been weighed up before, but it's finally time to at least pilot the system for a couple of weeks to see how it goes. If it doesn't work out according to plan, we'll revert to the older system or make modifications to this one.
To close your own thread:
At the risk of repeating myself, it must be a thread that you created. Click on "Thread Tools" in the thread toolbar (next to "Search this Thread"), then press Mark as Solved.
Abuse of this feature will be heavily monitored.