[sounds like] the coordinator would see the history of all transactions, since the private keys are not blinded like ecash tokens. Of course you can use a new key for each coin, but you could still be identified by IP address.

"the coordinator would see the history of all transactions, since the private keys are not blinded like ecash tokens"

The coordinator does not see the transactions he is signing. You give him something called a "sighash," which means you hash the tx and have him sign that hash. Consequently, he signs the hash "blindly," i.e. without knowing the preimage, and thus he cannot see the history of the transactions.

"Of course you can use a new key for each coin"

I do

"but you could still be identified by IP address"

The operator does not see your ip address because you communicate with him using nostr dms, and you use a different nostr key for every message