The Common Courtesy of Commenting

I browse a site called Quora now and then, it's basically a site where people ask questions for others to answer. It's not a bad site, and I enjoy answering questions for those who need help, providing I think I can answer with information that will really help them.
One of the questions I see repeated is about blog commenting. You see many of those asking questions are in internet marketing, and they have been told time and again if you comment on someone's blog, chances are they will comment yours and this can generate traffic(more visitors) to your site.
Well, that doesn't always work out the way they think it will, because many people are too self-absorbed and care only if someone comments on their blog posts, and usually they don't return the favor.
I comment on most of the blogs I take the time to read. If I can take 5 or 10 minutes to read a good post, at the very least I can take a few seconds to let the author know I read, I enjoyed, or I got happy or pissed off and let them know why. I think it's only common courtesy to do this. I don't comment for traffic.
If I was getting traffic from blogs I commented on I'd be all day reading the comments, which I wouldn't mind, even if it was time-consuming. 
Blog commenting to me is just that, a commentary of what I have read. Most bloggers consider any feedback good, even if the comment was to criticize the post. I've always appreciated any comments I receive, and try to always answer if necessary. It's just common courtesy!
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