Having multiple accounts isn't allowed and even if he had requested support to close his first account, he should have confirmed from them that his account is closed and he has opened a new one or at least should have asked permission to open the 2nd account. These things may seem small initially, but they can create problems specially if you have high balance in your gambling account and suddenly you found that your account is frozen because you violate the terms and conditions. I think in this case, he should be fine if he has proofs of all those conversion with the support team.
Duelbits is not that strict on multiple account before unless you are actively using both account to claim bonuses and participate tournaments.
I dunno if they change already their stance about this but I remember having dormant account there that I failed to report while I have active account that I’m actively using during events without encountering any problem.