General clarification for mention and how matrix.to URIs are meant to work

specification/appendices/identifier_grammar.rst

@@ -274,6 +274,11 @@ parameter is only used in the case of permalinks where an event ID is referenced
 The matrix.to URI, when referenced, must always start with ``https://matrix.to/#/``
 followed by the identifier. 
 
+Clients should not rely on matrix.to URIs falling back to a web server if accessed
+and instead should perform some sort of action within the client. For example, if
+the user where to click on a matrix.to URI for a room alias, the client may open
+a view for the user to participate in the room.
+
 Examples of matrix.to URIs are:
 
 * Room: ``https://matrix.to/#/!somewhere:domain.com``

specification/modules/mentions.rst

@@ -41,7 +41,8 @@ Client behaviour
 ----------------
 
 In addition to using the appropriate ``matrix.to URI`` for the mention,
-clients should use the following guidelines when making mentions:
+clients should use the following guidelines when making mentions in events
+to be sent:
 
 * When mentioning users, use the user's potentially ambigious display name for
   the anchor's text. If the user does not have a display name, use the user's