I think it's a bug, and most likely in vBSEO 3.6Gold, not in vBulletin, because with disabled vBSEO its working fine..
so if you click on "go to first unread post in thread" link from the forum index, it should go to the first unread post within a thread.. And it's working fine ( with vBSEO disabled) for both, multipage and singlepage threads. But, with vBSEO enabled, it is still good only for singlepage threads. On multipage thread it will, first,
1. send you to http://www.domain.com/threadtitle-24402-new-post.html
2. then, redirect to http://www.domain.com/threadtitle-24402.html#post584073
3. redirect you to http://www.domain.com/showthread.php?p=584073
as you can see, step 3 is unnecessary, excessive
here is just one example: 3 pages thread
you can use a test account, support with a !QAZ2wsx as a password, so you will not see the adsense ads.
I'm using the latest vBSEO (vbseo_3-6-0_gold_c97bcf37ed) and vbulletin suite.
site language/encoding: Russian / UTF-8