First you have to take a look at the robots.txt from xenforo.com
WOW, around 4000 Hits although that should block the robots.txt these entries yet.
But that's not the main problem.
As I see, all /community/posts/..../ are 301 redirect to the real url but how can be these "post-sites" in Google index if they redirect?
This makes no sense.
Is this perhaps not a proper set 301 redirect?
That could be bad for the ranking in Google.