Add extra note to pause-stop-hide understanding about multiple instances

understanding/20/pause-stop-hide.html

@@ -93,7 +93,7 @@ <h2>Intent of Pause, Stop, Hide</h2>
             auto-updating visual content. For audio content that starts automatically, refer to <a href="audio-control">1.4.2 Audio Control</a>.</p>
          <p>Moving, blinking, scrolling content that starts automatically because of a general user interaction (such as focusing/hovering over an element,
             or scrolling the page), rather than as a result of an intentional <em>activation</em> (such as activating a button),
-            and which doesn't provide a way to Pause, Stop, or Hide, will fail this Criterion, and potentially
+            and which doesn't provide a way to pause, stop, or hide, will fail this criterion, and potentially
             <a href="animation-from-interaction">2.3.3 Animation from Interaction</a>.</p>
       </div>
 
@@ -119,6 +119,15 @@ <h2>Intent of Pause, Stop, Hide</h2>
          </p>
       </div>
 
+      <div class="note">
+         <p>As a best practice, if a page contains more than one moving, blinking, scrolling, or auto-updating element,
+            provide a <em>single</em> <a>mechanism</a> to pause, stop, hide, or (in the case of auto-updating content)
+            control the update frequency that affects all these elements at the same time.</p>
+         <p>While having separate controls for each of the elements <em>does</em> satisfy the normative requirements
+            of this success criterion, this won't result in a good user experience for users, who will be forced to manually
+            pause, stop, hide, or control each moving, blinking, scrolling, or auto-updating element in isolation.</p>
+      </div>
+
    </section>
    <section id="benefits">
       <h2>Benefits of Pause, Stop, Hide</h2>