My understanding is it's not Agoracom, per se, that does the banning; rather, that task is given to the Hub Leaders. I can't see any reason why Silverback would have been banned for anything he said on this site. I tried to see what other sites he may have posted to, but see that his account has been entirely removed. Sad.
On another note, there are a LOT of posters with "silver" in their user name!
One other thing - I'm also given to understand that Hub Leaders have some influence in "restoring" banned members. I don't think they can do this directly, but I know of one banned user on another page that was restored when a Hub Leader made that request of Agoracom. Just saying.
M.
