Help sections and noticed a new commenting icon at the bottom of the page. It is the middle icon:
After doing some exploring I have found it does not appear on every page; it shows on about half. It seems to have cropped up with the new redesign of the Help Center along with other properties. You can see it in action at the bottom of this page and others. This commenting system replaces the "Was this information useful?" question.
My real surprise came when I clicked on the icon and a Google Sidewiki slide-out box opened from the left (screenshot below). Sidewiki has been around since 2009 as a Chrome extension to allow anyone to comment on any webpage and webpage owners to give special notes. It never gained much traction, but maybe it has found new life.
Could this be Google's answer to Disqus and IntenseDebate? With some tweaking, enhancements, expanded embedding options, and Google+ integration this could take over Facebook's commenting solution.