Potential scalability paradigms: UTXOs are more theoretically compatible with certain kinds of scalability paradigms, as we can rely on only the owner of some coins maintaining a Merkle proof of ownership, and even if everyone including the owner decides to forget that data then only the owner is harmed. In an account paradigm, everyone losing the portion of a Merkle tree corresponding to an account would make it impossible to process messages that affect that account at all in any way, including sending to it. However, non-UTXO-dependent scalability paradigms do exist.
I don't really understand the difference. In Bitcoin's UTXO paradigm, the owner of some coins must hold a private key for the destination address of an UXTO to prove ownership of the coins. If the key is lost, the coins are lost. As I understand, the same would happen in the account paradigm, except the owner would lose an account balance instead of an unspent transaction. What else would be lost in an account paradigm? How is that related to scalability?
Also, I understand what Merkle trees are and how they are used for storing transactions but what is a "Merkle proof of ownership"?
Thanks in advance.