watch_level_public_must_be_self· reason_code· applies to auth_decision`ak.strand.watch.set` writing `level_public=true` for another actor is rejected — publishing one's own subscription level is an opt-in personal disclosure and MUST be written by the target actor themself. `ak.strand.watch.set.others` writes MUST omit `level_public` or set it to `false`. See zh/models/strand-and-message.md §8.4.