Right, which is why in the article I linked, I describe a system that stores only the hash of the debtor's personal data on chain. A lender with the preimage can still use that to prove its case.

For stronger privacy we'd need ring signatures or zksnarks, so a person can't be identified by the flow of payments, but those technologies exist on various blockchains already.

you can use zeroknowledge proofs for things you don't want to reveal. it's called zk-snarks