Are they fully anonymous or not?
Because they say they're fully anonymous. You can't enforce a rule against multiple accounts at a fully anonymous casino. If they want to be a fully anonymous casino, they shouldn't allow the possibility for abuse from players using multiple accounts.
I am not a web developer to know how a website owner can check who visits his website. However, the simplest thing that comes to mind is that they just check IP.
You might say that 1xbit doesn't forbid the use of mutiaccounts - and that's right.
However, when someone is cheating, and the equivalent of the deposit has already been withdrawn from other accounts, in such case, for me it is a draw.
Now again the question is of who you believe.