Forum Moderators: rogerd
Trolls are tricky to deal with because often they don't violate your TOS in an overt manner. If they are outright spamming you, you can go to their ISPs with detailed info and have a good shot at getting them taken offline. If they are merely posting in a subtly provocative manner, though, it's a lot harder to get the ammunition you need.
I'd recommend tightening up your TOS to include a prohibition on any annoying behavior that is characteristic of this troll, including catch-alls like "failure to follow the instructions of a moderator" and "registering under more than one identity".
May not be possible in all cases, but it may be possible to find the source of their problem and deal with it there. In some cases, the troll is usually disgruntled over some preceived injustice, so resolving that injustice would stop the trolling.
Scott
Are you certain she is who she appears to be? In the anonymous world of fora, absent a registration that is validated by a credit card payment (I know they can be stolen) I'm reluctant to believe anyone's story without further evidence - like meeting them or knowing that someone else I know knows them, etc. This person could actually be someone intentionally sent to disrupt your affairs, a smaller version of a DDOS attack.
I'm afraid, with the worldwide connectivity of the WWW, we are going to see all manner of disreputable business practices. Though I believe you've got this one right, in believing it's a teenaged girl (the school is a pretty good tell, barring something more sophisticated) you just never know. I suspect fora will go through interesting times - just like search engines - as more people around the globe examine the financial impact of deploying, exploiting, manipulating or destroying fora.
Thanks for your help,
Teresa
P.S. That url was basically just saying, "send them to Miss Manners".
Cookies can be useful, but the surest method I've found at keeping out trolls is to put up significant barriers to entry. Sadly, this also greatly reduces the amount of new users you'll get. I've had major troll issues, so on my newest site I've put up significant barriers. This has kept us troll-free so far. For me, reducing the headache from undesireable users is very important. For someone who wants to grow their user base quickly, putting up significant barriers really isn't an option.