14

May I add comments to my Ribbon XML ? FAQ Link

Yes

Therefore use the following start tag :
<!--
and the following end tag :
-->

Sample XML: 

<customUI xmlns="http://schemas.microsoft.com/office/2006/01/customui">
<!-- This is a comment -->
   <ribbon startFromScratch="false">
      <tabs>
        <tab idMso="TabHomeAccess">
           <!-- This is a further comment -->
           <group id="myGroup" label="My Group" >
              <button id="myButton" label="My Button" imageMso="HappyFace"/>
           </group>       
        <tab>
      </tabs>
   </ribbon>
</customUI>