Sounds like a fiat payment problem than a trading platform problem. Like many others said, use irreversible fiat payment methods or fiat payments that are really hard to reverse.

I believe this is already being done in Bisq, no? As a buyer, you have to create a payment method for your account, and if the payment method is related to online bank transfers of some sort, you have to enter the name that is the same as the name in the fiat bank account. As a seller, you can verify that the fiat indeed came from a bank account with a matching name as the name on the payment method shown in Bisq. If there is a difference, you can always refuse to release coins and initiate mediation or even go to arbitration. Also, verification doesn’t happen on the account level, it happens on the payment method level. Each time a buyer adds a new payment method, that payment method needs to get re-verified (successful trade with another user with a verified payment method and wait 30 days), which means buyers can’t simply use “burner” payment methods.

At least above is the case for e-transfer payments methods in Canada. I have not used the Brazil payment methods, so don’t know if it different.