Why all bloggers want readers to post comments? Comments offer the blog both social and SEO benefits. Comments increase the percentage of text on the page. They increase the keywords, and hopefully, include a keyword anchored link to a webpage or blog with the same content and keywords.
But, rank in itself is of little importance to a blog. Social Networking, using Technorati, and del.icio.us, to promote the blog and pinging every new post, will do more to attract targeted readers than comments will.
Writing a blog that will target other bloggers has two benefits. Unofficial statistics suggest that bloggers leave more comments than non-bloggers. The authentication process does not offend them, and they can write a good comment. Bloggers are more likely to link back to your blog, or include a trackback. A trackback in the hands of a spammer can have detrimental effects, whereas a blogger can use a trackback to attract more readers and offer relevant material to their readers.
Search engines want new content. Most search engines drop old web pages from their searches, and some search engines drop pages after they are only a few months old. Comments change the page enough to keep the web pages content new. It is not a Black hat SEO trick to add your own comments, or to update a blog content. Adding new information is a legitimate method of increasing a web pages content, even if the information is included in a comment. A comment gives the blogger a second chance to include keyword relevant content in their blog. It also gives them a chance to address readers problems.
The comments increase the opportunity for a keyword anchored link back to related content. Make sure the keyword anchor copies the words used in the host blogs title and sub titles. Make sure the link back is to a blog with similar content. Do not leave a comment unless you have something valid to say. Do not leave comments like Great idea.
A blogger who leaves comments in another blog will be more inclined to link to that blog. Many bloggers will reply to a similar blog and then include a keyword-anchored link to that blog. This gives their blog credibility and makes the bloggers opinions appear more legitimate.