Wrong! Activity updates only if you make atleast 1 post in 2 weeks period. It is same for trust rating, it will only increase if a person from DefaultTrust list or on a user's trust list put a trust feedback.
-MZ
If your post count is below your activity points(activity points you can use) you must post more to see your activity count increase. Your activity point is like a limit, limit increases as more active 2 weeks period you gain. People not from your trust list will not appear as trusted feedback but as untrusted feedback. Trust list is different for everyone if they modify it so trust rating will appear differently.