Reword some of the discussion and put in non-normative note.

Author: mgiuca

mediaqueries-5/Overview.bs

@@ -1333,9 +1333,10 @@ Display Modes: the ''display-mode'' media feature </h3>
 	This media feature reflects the actual [=display mode=] that is being used on the current browsing
 	context, not necessarily the one that was requested in the web app manifest (if any).
 
-	On normal web pages, 'display-mode' will have a value of ''browser''. Only pages appearing in the
-	context of an [=installed web application=] can have a different 'display-mode', reflecting the
-	way in which the application window is being presented to the end user.
+	Note: When a page is being displayed in a normal web browser, 'display-mode' will always have a
+	value of ''browser''. Only pages appearing in the context of an [=installed web application=] will
+	have a different 'display-mode', reflecting the way in which the application window is being
+	presented to the end user.
 
 	<details class="note">
 		<summary>The [=display mode/fullscreen=] [=display mode=] is distinct from the [[FULLSCREEN|Fullscreen API]].</summary>