Pivot away from MSC3440: Threads

content/client-server-api/_index.md

@@ -1877,6 +1877,10 @@ forming a sort of chain of events.
 This specification describes the following relationship types:
 
 * [Rich replies](#rich-replies)
+<!--
+TODO: TR,MSC3440: Uncomment for threading support.
+* [Event threading](#threading)
+-->
 
 ## Rooms
 

content/client-server-api/modules/rich_replies.md

@@ -51,10 +51,13 @@ An example reply would be:
 Note that the `event_id` of the `m.in_reply_to` object has the same requirements
 as if it were to be under `m.relates_to` directly instead.
 
+<!--
+TODO: TR, MSC3440: Uncomment for threads support
 {{% boxes/note %}}
 Some event relationships, like [threads](#threading), describe what it looks like
 to both form a relationship *and* still reply to another event.
 {{% /boxes/note %}}
+-->
 
 #### Fallbacks for rich replies