With a new update to Google's systems a couple days ago, I can now comment on reviews/ratings that are left in the market!
This is great, because there are a couple of reviews which are requesting features that are now available in newer versions, and I can comment saying that the feature has been added. Also, I was able to leave an explanation to the one negative comment I received, and hopefully people will see my comment and realize that the negative review was left due to user error, not an error on the program's part. (I also said to email me if there are still issues with that review.)
The only thing I'm not sure of, is if the user is alerted that I have commented on their review. This would be nice, because it could cause some users to then update their review to reflect the comments that I left.
If any of you left a review which I commented on, let me know if you get a notice of my comment. :-)