Hello ronran.
Thank you for your inquiry. Yes our system applies to all HUB's. So if a member is banned on HUB "A", that member will also be banned from HUB's "B" and "C" and etc.
Unfortunately our site is not equipped to make it as such that a member cannot post on one HUB over the other.
We appreciate your understanding and your participation within the AGORACOM Community.
Regards,
AGORACOM