In your OP, you didn't mentioned about Commentluv, you only asked about "Comment sites" Right?
However, if your question was related to Commentluv, then here is the answer to your question.
"Commentluv" a wordpress plugin used to enhance your Wordpress blog, with comments, social sharing your blog comments and your posts to get viral. It also includes anti-spam feature to prevent spammers/automated bots which helps to prevent the spam from your blog.
Few websites and blog provides facility for posting or sharing your view about subject already published such kind of website is known as commenting sites that play an strong role in Google search results and relevant targeting audience at websites.
Blog commenting is one in every of the best and simplest ways in which to urge free a technique links to your web site. this easy technique of advertising your business on-line will generate vital leads to terms of SEO. With comment spam being one in every of the most problems targeted with Google's penguin update, several webmasters are curious if journal commenting may be a worthy link building strategy.
Blog Commenting is also an another off page SEO activity for website promotion. It is a very good source of diverse links back to your site. Blog commenting simply to put your views on related article or post. Blog commenting really helps you to increase your web traffic and rankings as well.
yes this is possible to post comments on dofollow blogs and get backlinks, but your comments must be intersting - not just "wow! nice post, thanks"
not moderated blogs have tons of coments and moderated blogs are removing spam posts
in blog interesting and relevat to your website, then you really able to get quality convertable traffc
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Comment Site is getting DoFollow Backlinks to Your Website and thus Increasing Traffic for Your Website. Building Backlinks is a very Important Part for every new Website or Blog as it will help you in Improving Google Search Rankings as well Alexa Ranking.