[css-2015] Clarifications per www-style discussion

Author: fantasai

css-2015/Overview.bs

@@ -424,12 +424,16 @@ Requirements for Responsible Implementation of CSS</h2>
 
 			Issue: Added "should not" against encumbered features, per dbaron's request.
 
-			If at least three UAs implement a feature
-			(or if a browser has broken the previous rule and shipped for broad use
-			an <a>unstable</a> or otherwise non-standard feature in a production release),
-			and the implementations have rough interoperability,
-			<em>and</em> the CSS Working Group has recorded consensus that this feature should exist and be released,
-			implementers may ship that feature unprefixed in release builds.
+			If a feature is <a>unstable</a>, yet
+
+			*	at least three UAs implement the feature
+				(or a browser has broken the other rules and shipped for broad use
+				an <a>unstable</a> or otherwise non-standard feature in a production release),
+			*	<em>and</em> the implementations have rough interoperability,
+			*	<em>and</em> the CSS Working Group has recorded consensus
+				that this feature should exist and be released,
+
+			implementers may ship that feature unprefixed in broad-release builds.
 			<dfn>Rough interoperability</dfn> is satisfied by a subjective judgment
 			that even though there may be differences,
 			the implementations are sufficiently similar
@@ -494,7 +498,7 @@ Requirements for Responsible Implementation of CSS</h2>
 
 			<div class="example">
 				For example,
-				Win8 Metro apps, Firefox's XUL-based UI, and the iTunes UI
+				Firefox's XUL-based UI, Apple's iTunes UI, and Microsoft's Universal Windows Platform app
 				use extensions to CSS implemented by their respective UAs.
 				So long as these UAs do not allow Web content to access these features,
 				they do not provide an opportunity for such content