A couple of clarifications

- the body of the tombstone is defined by the server.
- the client can follow tombstones until it finds a live room

proposals/1501-room-version-upgrades.md

@@ -77,10 +77,13 @@ When this is called, the server:
    }
    ```
 
+   The `body` of the tombstone event is defined by the server (for now, at
+   least).
+
  * Assuming Alice has the powers to do so, sets the power levels in the old
    room to stop people speaking. In practice, this means setting
    `events_default` and `invite` to the greater of `50` and `users_default+1`.
-   
+
 Bob's client understands the `m.room.tombstone` event, and:
 
  * Hides the old room in the room list (the room continues to be accessible
@@ -96,6 +99,10 @@ Bob's client understands the `m.room.tombstone` event, and:
    for a while and eventually fails. Synapse 0.33.3 should at least give a
    sensible error code.]
 
+   If it turns out that the replacement room also has a tombstone event, the
+   client may automatically keep following the chain until it reaches a room
+   that isn't dead.
+
  * Optional extension: if the user is in both rooms, then the "N unread
    messages" banner when scrolled up in the old room could be made to track
    messages in the new room (so in practice the user would only ever see the