Sorry to see you go.
If you use the IP tool above you can determine if a user is is logging in under diferrent aliases. You might think OPC is using multiple aliases but it would take a lot of work to change locations and log in again.
They say paranoia will destroy you.
I wish we could block IP's on the Yahoo! board because it is my theory there are about 1-2 people who constantly create aliases and fill that board with trash.