Actually, I prefer using a thread icon (like a tick) which the user could change manually by editing his first post, or with a button located in the thread.
This method is used in
VBForums.
When his/her question is anwsered, the thread creator edits his/her post and change the topic icon, and if he/she wants, she/he can add "[Solved]" to their thread title.
Here's how the icon looks:
![[Image: completeclear.gif]](http://mike.thedt.net/images/temp/completeclear.gif)
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