Earlier quoted context omitted.
That doesn't work. They are perfectly happy to revel in the attention of their friends. http://freethoughtblogs.com/almostdiamonds/2012/02/28/dont-f...
This is what caused me to wonder if allowing trolls, but eliminating their conversation from everyone but other trolling users might be an option. Let them revel in the attention of their friends, but have that attention only serve to give them the illusion that they're affecting others while directly causing others to ignore them (and thus, prevent unintentional feeding). It'd be tricky to get right and probably not…
It's an interesting idea (and I'm 100% sure it's been done before), but it doesn't really work out on any site with a significant audience. I mean, all you need is one of those trolls to access the site at work/school/wherever and notice their posts are being shown if they're not logged in, and then suspicions are raised.
Too easy to bypass and figure out. It's like how people figured out Twitter's shadowbans, because people who followed them said off site that they weren't seeing their messages.