This is one of those questions that comes up a lot. The short answer is do what works best for you.
The long answer (you knew it would be so easy, right?) is that every blogger handles this differently. Some bloggers answer comments by writing their comments under the first comment. Some bloggers respond via e-mail (if you’ve included your e-mail in your comment). If it’s a recurring question or comment, a blogger may choose to post an update to the original post. Still others choose not to respond at all.
Regardless of how you choose to respond to comments, please do not take it personally if a blogger does not respond to yours. It’s true that leaving and responding to comments is a great way to become a part of the blogging community. It can also help you build your traffic; if people feel they are being heard, they will most likely continue to visit your site. However, some sites have such a high volume of comments that it’s impossible to answer each comment.