[css-fonts-4] Improve font fallback on font-variant-emoji with variation selectors, w3c#9291

Author: svgeesus

css-fonts-4/Overview.bs

@@ -7873,10 +7873,14 @@ however, the exact nature of the interaction of font fallback with 'font-variant
 is explicitly unspecified.
 However, a variation selector must be included in a previous cluster
 as defined by the <a href="#cluster-matching">cluster matching</a> section above.
-Therefore, the presence of a variation selector
-is treated as ancillary data to inform the font fallback routine.
 A natural result of this behavior
 is that a variation selector must not be rendered in a different font than the previous character.
+It thus causes font fallback to behave 
+as if the respective variation selector was intended 
+(as in the values description); 
+then font fallback, including the cluster fallback rules, is performed, 
+which must take the presentation preference
+of these "appended" variation selectors into account.
 
 Even when 'font-variant-emoji' is used,
 the presence of Variation Selector 15 (U+FE0E) or Variation Selector 16 (U+FE0F)