Incorporate review

Author: babolivier

proposals/3720-account-status.md

@@ -78,11 +78,14 @@ federation endpoint described below.
 Below is how this endpoint behaves in case of errors:
 
 * If no `user_ids` field is provided, the endpoint responds with a 400 status
-  code and a `M_MISSING_PARAM` error code.
+  code and a `M_BAD_JSON` error code.
 * If one or more of the user ID(s) provided cannot be parsed as a valid Matrix
   user ID, the endpoint responds with a 400 status code and a `M_INVALID_PARAM`
   error code.
 
+If the `user_ids` field is an empty list, the server responds with a `200 OK`
+status and an empty body (`{}`).
+
 ### `POST /_matrix/federation/v1/account_status`
 
 This endpoint behaves in an identical way to the client-side endpoint described