Is there a point in going round blogs dumping your link in comments? Does this actually generate any traffic or link popularity and ranking google?
If you post intersting comment then it is definitely worth your time, but if you are going to write in all comments: visit my site www.site.com then this is a waste of time, such comment will proboably never be published and even if it will then no one would ike to visit spammer site.
You need to make sure you contribute to the blog with quality, relevant and to the topic comment and don't just spam the blog for the sake of a link. If your post is worthwile and helpful it will be approved and you might get some traffic through that link.