Reference m.room.member section

specification/modules/dm.rst

@@ -36,10 +36,11 @@ Events
 
 Client behaviour
 ----------------
-The invitee's client may use the ``is_direct`` flag to automatically mark the
-room as a direct message but this is not required: it may for example, prompt
-the user, ignore the flag altogether. To do this, it stores this event in
-account data using the ``account_data`` API: see `Client Config`_.
+The invitee's client may use the ``is_direct`` flag in `m.room.member`_ to
+automatically mark the room as a direct message but this is not required: it
+may for example, prompt the user, ignore the flag altogether. To do this, it
+stores this event in account data using the ``account_data`` API: see `Client
+Config`_.
 
 The inviter's client should set the ``is_direct`` flag to  ``createRoom``
 whenever the flow the user has followed is one where their intention is to