Okay, when farming the charms at the bunnycave - Farmed them crossrealm on a lowpop server, i met a friend of mine(from my own server, but he too was on that server).
I left combat, and so did he, we went outside the cave and i attempted to trade him a few uncut gems, which he was going to cut for me.
As i put in the gems, and clicked trade, the guy who i was CRZ'ing with, left the party. The trade said "Complete" i looked in my bags(cause the bagspace number didnt get any less) and saw the Grayed out Gems, i relogged and they weren't grayed out anymore.
I asked my mate if he had gotten the gems, and oh yeah he had, he cut them, and mailed them to me
So what you need for this to work:
4 Accounts; A1, A2 & B1,B2.
Note that both A2 and B2 Should be from the same realm, along with A1 and B1 Being on the same realm.
Find eachother and open a trade.
Put in anything you want duped
Now the hard part; click trade on the exact same moment your mate leaves group, and you get ported back to your own server.
Relogg and enjoy duplicated items.
I found this yesterday, and since that i havn't been able to recreate it, as i found it by coincidence.
Enjoy, though i advise you to not use this from your main account