Their official response has so far been 'No Comment' but in fact there is reason to believe that a Google+ based commenting system is in the works. The Next Web was able to get unofficial confirmation of the news that emerged from a Google Event in Saudi Arabia describing a Google+ commenting system that would be compete with the year old Facebook comment plug-in. According to analysis from EdgeRank Checker a Facebook Comment can produce 4x as many clicks as a Like.
ReadWriteWeb looked at the pros and cons of handling comments via a social network's plug-in and saw a problem if it did not open comments to users who were not a member (or did not want to reveal their membership) in a particular network. Certainly the implied advantage of the Google system is better ranking for the comments.
Facebook also made some news on the commenting front this week, upgrading features relating to moderating and providing permalinks.