MyBB Community Forums

Hello,
If you set your MYBB url structure to search engine friendly, the URL structure would become something like http://community.mybb.com/thread-1234.html
Now the problem is that http://community.mybb.com/showthread.php?tid=1234 will render the same page as the above and the url will remain http://community.mybb.com/showthread.php?tid=1234
IMO, this is setting Webmasters up for duplicate content.
I think once set to seo friendly format, all URLs in the old format should 301 redirect to the SEO friendly format.

I believe that MyBB uses canonical URL structure, so single url will not be counted as duplicate structure.

If you like, Google SEO plugin will do those redirects and canonicals for you.