twinkle-pagestyles.css: expand comment (wikimedia-gadgets#1893)

twinkle-pagestyles.css

@@ -1,7 +1,9 @@
 /**
  * This is loaded as a hidden peer gadget of Twinkle.
- * Before core Twinkle has loaded, it adds space where the TW would go in the
- * Vector skin, so that the top bar does not "jump".
+ * Why is this a peer gadget? Because it will load before the page finishes its first paint.
+ * It adds whitespace where the "TW" menu goes in the Vector 2010 skin, basically reserving
+ * a spot for the "TW" menu so that the top bar does not "jump".
+ * The "TW" menu itself is painted later, after the gadget JS files finish loading.
  */
 .client-js > body.skin-vector:not(.ns-special) #p-cactions,
 .client-js > body.skin-vector.mw-special-Block #p-cactions,