Improve generic reposts for replaceable events (#2132)

18.md

@@ -1,8 +1,6 @@
-NIP-18
-======
+# NIP-18
 
-Reposts
--------
+## Reposts
 
 `draft` `optional`
 
@@ -21,9 +19,9 @@ reposted.
 
 ## Quote Reposts
 
-Mentions to [NIP-21](21.md) entities like `nevent`, `note` and `naddr` on any 
-event must be converted into `q` tags. The `q` tag ensures quote reposts are 
-not pulled and included as replies in threads. It also allows you to easily 
+Mentions to [NIP-21](21.md) entities like `nevent`, `note` and `naddr` on any
+event must be converted into `q` tags. The `q` tag ensures quote reposts are
+not pulled and included as replies in threads. It also allows you to easily
 pull and count all of the quotes for a post. The syntax follows
 
 `["q", "<event-id> or <event-address>", "<relay-url>", "<pubkey-if-a-regular-event>"]`
@@ -36,3 +34,10 @@ as a "generic repost", that can include any kind of event inside other than
 
 `kind 16` reposts SHOULD contain a `"k"` tag with the stringified kind number
 of the reposted event as its value.
+
+When reposting a replaceable event, the repost SHOULD include an `"a"` tag with
+the event coordinate (`kind:pubkey:d-tag`) of the reposted event.
+
+If the `"a"` tag is not present, it indicates that a specific version of a replaceable
+event is being reposted, in which case the `content` field must contain the full
+JSON string of the reposted event.