OK, let’s continue.

kind1059(kind13(kind14)) VS kind1059(kind1)

In the kind1059(kind13(kind14)) model, if the recipient discloses the encryption key, not only will the sender's messages be visible to everyone, but the recipient's own messages will also be visible to everyone. This is disadvantageous for the recipient and advantageous for the sender. In the kind1059(kind1) model, if the sender discloses the unencrypted kind1, everyone can see the messages sent by the sender. However, the sender can also proactively disclose the messages previously sent by the recipient. Furthermore, the sender can identify who disclosed the messages, which is a good thing. In both cases, the sender can determine who disclosed the messages.

Finally, regarding the issue of app bugs causing kind14 leaks, it would require extremely poor code quality for this to happen. If you must consider this risk, why not directly encrypt the content using NIP-44? Using kind4(kind4) would be simpler than kind1059(kind13(kind14)). Please note that the kind4 mentioned here uses NIP-44 encryption, not NIP-4 encryption.