Just realized I didn't know this: how are you supposed to comply with GDPR if your clients are partially anonymous?
But in this case, I'm assuming the user must have a private key (for signing BAT transactions), so they could build a feature in the browser to sign messages using it.
https://github.com/brave-intl/bat-ledger/blob/master/documen...
The current process is the data is anonymized and then sent out for privacy reasons.