When you respond to your comments you have a great opportunity to form a relationship with that person. To do this you need to address their comment as though you were chatting with your best friend.

If there is an opportunity to ask them a question and encourage them to leave a reply then do it. For example if they ask you about the food value of the dog food you are selling you can ask them about their dog. What breed, how old etc. You could tell them about your dog. Try to get an interaction going so you can get to know each other.

This can get them back to your site to answer your questions. More traffic, more content and possibly even some sales.

The type of comments you get gives you insight into who this person really is. Often they inadvertently give their age away, their marital status, how many children, their interests, their pet hates etc. Don't just look at the surface of your comments dig deeper to try to find the real person who wrote it. That is your target audience.