Patting myself on the back
I reply to every review, either on site, or through a private message in which I leave my e-mail. I am fortunate in that the reviewers of my stories have all been articulate in their comments. I encourage the exchange of ideas, and as several members of this site will attest, I listen to comments and have revised my stories accordingly.
As I have said elsewhere too, I do not post any stories on this site until they have been critiqued by a small group of people whose opinions I trust to be honest and forthright - if he/she doesn't like it, I hear about it, and why.
As a writer, I have a responsibility to thank the reviewer. I do not have to agree, but this person has taken the time to comment on my work, and I shouold acknowledge their interest in my writing, even if it is just being polite. We as a society have lost much of our good manners, but that's a whole different thread.