diff --git a/lib/legacy/polymer.dom.js b/lib/legacy/polymer.dom.js
index cf5c1ddc66..6d7f0eb667 100644
--- a/lib/legacy/polymer.dom.js
+++ b/lib/legacy/polymer.dom.js
@@ -395,6 +395,8 @@ if (window['ShadyDOM'] && window['ShadyDOM']['inUse'] && window['ShadyDOM']['noP
     }
   });
 
+  // Note, `classList` is here only for legacy compatibility since it does not
+  // trigger distribution in v1 Shadow DOM.
   forwardReadOnlyProperties(Wrapper.prototype, [
     'classList'
   ]);
@@ -420,12 +422,17 @@ if (window['ShadyDOM'] && window['ShadyDOM']['inUse'] && window['ShadyDOM']['noP
 
 } else {
 
+  // Methods that can provoke distribution or must return the logical, not
+  // composed tree.
   forwardMethods(DomApiNative.prototype, [
     'cloneNode', 'appendChild', 'insertBefore', 'removeChild',
     'replaceChild', 'setAttribute', 'removeAttribute',
     'querySelector', 'querySelectorAll'
   ]);
 
+  // Properties that should return the logical, not composed tree. Note, `classList`
+  // is here only for legacy compatibility since it does not trigger distribution
+  // in v1 Shadow DOM.
   forwardReadOnlyProperties(DomApiNative.prototype, [
     'parentNode', 'firstChild', 'lastChild',
     'nextSibling', 'previousSibling', 'firstElementChild',