Of course they don't have to, but maybe they should, otherwise it really looks a little strange.
I just looked over their TOS and it states:
7. PLAYER ACCOUNT
7.1 Each player can create only one personal user account. There can be no more than 1 account created per household, IP and device. Creating multiple user accounts will lead to termination of the accounts. All betting accounts you try to open may be blocked or closed and any bets may be voided. Depending on the severity of the case Betcoin.ag holds the right to withhold or take any funds deposited to pay for damages and/or the prevention of future misconduct.
We are talking about 1 LTC, 70$. I don't see any severity in this case. Also they didn't state if he abused any promotions or any other new player offer which would have given him an advantage. That is actually the most important question n this case.
They already explained the issue and they also said their previous comment is the last here in this case. So I don't think they will come back again here to explain.
On the other hand, I don't think the severity does not only depend on the amount, you know multiple accounts are highly provided by every casino nowadays. And of course, Most of the abusers try to create multiple accounts to become under the radar. Maybe they take it seriously and take the action.
