I don’t think it’s as simple as changing the name of the merchant anymore. I think each merchant probably has some type of account number, and the banks probably flag the account or merchant id as selling online casino chips.
The most impressive experience I ever had in this regard was at Party Poker. I tried to make a deposit with my debit card, it declined, and my phone rang. It was Party Poker, who walked me through the process of getting a prepaid phone card to fund my account with. It was a very good experience, and one that I’m sure contributes to their high conversion rates.