[css-display-3] Be more specific in the warning note about 'visibility'. w3c#6123

Author: tabatkins

css-display-3/Overview.bs

@@ -1130,12 +1130,14 @@ Invisibility: the 'visibility' property</h2>
 			just like ''visibility/hidden''.
 	</dl>
 
-	Note: For certain constructs with strict hierarchical structure
-	such as tables
-	making parent elements with special roles (such as table rows) [=invisible=]
+	Note: Currently, many user agents and/or accessibility tools
+	don't correctly implement the accessibility implications of
+	visible elements contained within [=invisible=] elements,
+	so making parent elements with special roles (such as table rows) [=invisible=]
 	while leaving child elements with special roles (such as table cells) visible
-	can be problematic for accessibility tools.
-	Authors should avoid creating these situations.
+	can be problematic for users of those tools.
+	Authors should avoid creating these situations
+	until the tooling situation improves.
 
 	<dfn>Invisible</dfn> boxes are not rendered
 	(as if they were fully transparent),