It looks like we'll soon be able to answer to comments in the market by sending email to the author.
Go in your developer console, comment section, and use Chrome inspect element function on a comment. You'll see two buttons hidden. Edit dynamicaly the style and remove the display:none
You'll see two buttons: one to answer the comment, and another to see the answer we sent. If you click on the "answer" button you'll get a popup inviting you to enter your answer and it will be sent to the user by email.
Here are two screenshot (in French, sorry, but you see the idea)
Unfortunately, the function seems not to be active right now, as it shows an error when you try to send an answer. But it looks that soon we'll be able to do that, which is an excellent news.