Improve comment.

Author: kevinpschaaf

src/lib/template/templatizer.html

@@ -198,8 +198,11 @@
     },
 
     _customPrepAnnotations: function(archetype, template) {
-      // Store a "clone" of the template on the archetype (content has been
-      // pulled into _content property, so copy that also)
+      // Store a "clone" of the template on the archetype to ensure no
+      // references on this template are leaked onto the cached archetype
+      // Note we don't actually clone the template since it could be
+      // a type-extension; rather we create a new one and copy the
+      // `_content` reference holding the prototypical content over
       var t = archetype._template = document.createElement('template');
       var c = t._content = template._content;
       if (!c._notes) {