I don't remember exactly when NodeReaper gained the ability to shut people out of chatter.

The two essential infrastructural nodes were created on 2001-02-02. One, borged users, is the data table containing whatever users are borged at the moment. The other, Borg's Belly, displays that data table. At that time, only gods (presumably) were able to add and delete users in that table. Five days later, the power users group was created, so that specially deputized users other than gods could keep the cb decent.

Alex the Serb joined on 2001-05-27. He didn't post until December of that year, and it's possible he wasn't otherwise active on the site until that time.

There were some significant changes (upgrades) in the borg-related infrastructure in 2002-06.
(Book 'em, Danno - nodelet for the power users group (unused); message - (patch) - implements borg'y stuff; borg - executes the borg command.)
It's possible, I guess, that these were motivated by a surge in troll activity.