WIP: improve comment

Author: petebacondarwin

src/ng/directive/select.js

@@ -42,10 +42,13 @@ var SelectController =
     if (self.unknownOption.parent()) self.unknownOption.remove();
   };
 
-  // The "empty" option is one that has a value of '' and can be provided as a child of
-  // the `select` element.
-  // In the basic select, we only need to use this to make IE9 happy when we set the select's
-  // value to '', but also ngOption uses this for its own purposes too.
+  // Here we find the option that represents the "empty" value, i.e. the option with a value
+  // of `""`.  This option needs to be accessed (to select it directly) when setting the value
+  // of the select to `""` because IE9 will not automatically select the option.
+  //
+  // Additionally, the `ngOptions` directive uses this option to allow the application developer
+  // to provide their own custom "empty" option when the viewValue does not match any of the
+  // option values.
   for (var i = 0, children = $element.children(), ii = children.length; i < ii; i++) {
     if (children[i].value === '') {
       self.emptyOption = children.eq(i);