diff --git a/lib/utils/debounce.html b/lib/utils/debounce.html
index ad6b98ff95..54fc859623 100644
--- a/lib/utils/debounce.html
+++ b/lib/utils/debounce.html
@@ -127,6 +127,8 @@
    * @return {void}
    */
   Polymer.enqueueDebouncer = function(debouncer) {
+    // Re-enqueued debouncers are put at the end of the queue; for Set, this
+    // means removing and re-adding, since forEach traverses insertion order
     if (debouncerQueue.has(debouncer)) {
       debouncerQueue.delete(debouncer);
     }
@@ -135,6 +137,8 @@
   
   Polymer.flushDebouncers = function() {
     const didFlush = Boolean(debouncerQueue.size);
+    // If new debouncers are added while flushing, Set.forEach will ensure
+    // newly added ones are also flushed
     debouncerQueue.forEach(debouncer => {
       try {
         debouncer.flush();