migrate nips from main nostr repo.

09.md

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+NIP-09
+======
+
+Event Deletion
+--------------
+
+`draft` `optional` `author:scsibug`
+
+A special event with kind `5`, meaning "deletion" is defined as having a list of one or more `e` tags, each referencing an event the author is requesting to be deleted.
+
+Each tag entry must contain an "e" event id intended for deletion.
+
+The event's `content` field MAY contain a text note describing the reason for the deletion.
+
+For example:
+
+```
+{
+  "kind": 5,
+  "pubkey": <32-bytes hex-encoded public key of the event creator>,
+  "tags": [
+    ["e", "dcd59..464a2"],
+    ["e", "968c5..ad7a4"],
+  ],
+  "content": "these posts were published by accident",
+  ...other fields
+}
+```
+
+Relays MAY delete or stop publishing any referenced events that have an identical `pubkey` as the deletion request.  Clients may hide or otherwise indicate a deletion status for referenced events.
+
+## Client Usage
+
+Clients MAY choose to fully hide any events that are referenced by valid deletion events.  This includes text notes, direct messages, or other yet-to-be defined event kinds.  Alternatively, they MAY show the event along with an icon or other indication that the author has "disowned" the event.  The `content` field MAY also be used to replace the deleted events own content, although a user interface should clearly indicate that this is a deletion reason, not the original content.
+
+A client MUST validate that each event `pubkey` referenced in the `e` tag of the deletion request is identical to the deletion request `pubkey`, before hiding or deleting any event.  Relays can not, in general, perform this validation and should not be treated as authoritative.
+
+Clients display the deletion event itself in any way they choose, e.g., not at all, or with a prominent notice.
+
+## Relay Usage
+
+Relays MAY validate that a deletion event only references events that have the same `pubkey` as the deletion itself, however this is not required since relays may not have knowledge of all referenced events.
+
+## Deleting a Deletion
+
+Publishing a deletion event against a deletion has no effect.  Clients and relays are not obliged to support "undelete" functionality.