Unregistering a linkshell on your LS Community Website:
Be sure it is not the linkshell you associated your ffxiah.com account, if you are in a ls and want the information from your current ls, copy/paste the link of your profile under the linkshell you are in under edit chars on ffxiah.com.
However I believe Scragg has fixed it for linkshells not to be auto-scanned in, but this would be for future if it happens again. :)
To unregister:
Go to the LS Community site http://fanzone.playonline.com/lscom/index.do
Select the linkshell (Make sure its the one not associated with your FFXIAH.com Account)
Click on Member Profile Editor
Then Select Cancel Membership Registration on bottom of your profile for the Linkshell you selected.
Confirm you really want to unregister the linkshell.