I definitely am, they must have been registered to the email before the "one account per email" thing got put into place, otherwise you wouldn't be able to.
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The bigger use of alts is dueling and anonymity, if a player has a bad reputation or wants to duel someone that wouldn't normally duel them, use an alt account. Don't remove the availability for alts all in all, MAYBE make it a bit more complicated to make alts, as in email verification, but I don't see a big need to do so. Duelers aren't going to target beginner servers, they're going to go to private servers and public servers and duel. Players wanting anonymity are not going to target beginner servers because there's no fun in beating people that can't challenge you. The only real reason people might go to beginner servers on alts that I can see would be to gain a little amount of qi and then leave for whatever reason, which is where the server squatters come in.