It is mysterious if Duelbits team haven't blocked your account completely despite knowing about your multiple accounts.
Maybe because I wasn't breaking any TOS? It could also possible that I was winning from the leaderboard and they don't want a winning customer. Who knows only DB can answer those questions because when I asked support they only provided me a generic response that excluding me was from the decision of their marketing dept.
As @avp2306 and @mahdirakib alters pointed out, clearly you violated the casino ToS on multiple account.
However, you are not abusing their bonus that’s why they let you off the hook rather just exclude you from marketing which is not new even for single account user only that frequently winning through their tournament and bonuses.
Most casino don’t reinforce immediately the multiple account policy if you don’t use it to abuse casino promotion.
But they likely will reinforce much later when you least expect it, mostly when luck hits you so hard that you win a very large amount of money and requesting withdrawal from the Casino, then and only then, the casino will go back and dig out your past sin and reasons why they can't grant your withdrawal request..
Gamblers ought to be learning from other gambler's experiences and avoid whatever will end up being a problem for them in future, casinos are out here to make money and it's mostly painful for most of them to lose huge amount to users, and when they see any opportunity not to pay a user, they quickly will grab it.