This issue is not solved in MyBB 1.2.7 yet. It's still using many queries to obtain is_moderator forums and subforums. You can take a look here. I created some forum for testing.
http://vmk.110mb.com/demo/mybb/forum/index.php?debug=1
(The testing forum is on a free server which is not stable, You may have to try some times to reach this page)
http://vmk.110mb.com/demo/mybb/forum/index.php?debug=1
(The testing forum is on a free server which is not stable, You may have to try some times to reach this page)