I do feel that comments matter. For me, I often post on my blog and wonder if anyone is actually reading it. Having even one comment on a post keeps my motivation up, keeps me remembering to write a new blog entry. I recently wrote a review of a non-fiction narrative that my book club read. I mostly posted it on my blog to work through how I felt about the book. The next day, the author of the book commented on my blog. Amazing. Her comment made my week, maybe my month. Commenting on each other's blogs can be a very positive way to support other writers. You never know how happy you might make someone feel.