I'm sure Millard knows this being he's familiar with Xenforo, but there are all kinds of add-on's that can detect multiple accounts. Fancy scripts etc that can detect if you or I have decided to make another account. I won't say how they work, because that's handing the key's to the convicts, but, there are ways to detect multiple accounts.There's 3 ways to detect scripts AFAICT:
Rapid fire posting attempts can be a sign of a script or bot, but as there's flow control (30 secs between posts), you can perhaps see if there's multiple posting attempts despite the flow control.
- Out of sequence or too-frequent AJAX requests.
- Changes to the page's code (HTML, global JS, or even CSS).
- Unnatural mouse or keyboard action.
The server logs or Xenforo logs may have such info.
I own 2 forums, both use Xenforo. You can either use 3rd party add-on's and or hire a programmer to make some custom scripts for you to make what you need. Or if you really know how to write scripts, do it yourself.
Another thought completely off topic, how the hell do you see who's banned and who's not? When I ban someone it shows up on the user profile right away. What am I missing?