Omg omg omg omg omg!!!!
That's how I'm feeling at the moment. On to the exploit.
I were transferring a few characters using the free character migration. By mistake I returned a mail to a character "in transfer" and bam! I had the character on both servers.
To be sure that it worked I tried again ( this time I just sent a mail to the character instead of returning one) and now I had another pair of the same character, I also tried a third time but that one failed. I guess it could have been that the transfer completed before I could send the mail.
So the exploit worked 2/3 times.
I have no idea if it works with the normal character transfer, I've only tried with the free version.
If this really works, have fun!
Step by step guide
1. Start character transfer
2. Send in-game mail containing an item to the character "in transfer" This has to be done before the transfer is complete.
3. Enjoy having a copy of your character.