People don’t leave comments just so they can be left unread. By replying, you’re not only letting people know that you’re actively involved in reading the comments, but you’re encouraging them to come back and comment again later.
A reply can often lead to side conversations within the commenting area that add to the content and overall quality of your post.
More comments, including your own, usually mean more instances of the keywords that you used in your blog post, which means you’re more likely to be found in the search engines for those terms.
Social proof is a psychological phenomenon that occurs when people’s decisions are influenced by making the assumption that surrounding people know more about certain situations than you do.
Finally, by responding to each comment, you’re establishing yourself as a go-to expert in your niche.