It is important to comment on a blog post because it gives the author/writer some great feedback that can guide their future work. However if your comment is not one of greeting or related to the topic being discussed in then perhaps one should just get offline and do something else with your time. Comments on the posts topic is a sign you are paying attention. None of you who follow me do that but there are spammers who like to do that sort of thing. Keeping on point is a wonderful thing though.