I got new friend thorugh my blog. How to do that? I saw their comment on my blog and i replied them. So branding your comment on other blog can increase your traffic and make you have a new friend too. Why give a comment on other blog can increase your traffic?
If you commented on other blogs and not do SPAM, maybe some people that visit that blog will be interest with your comment, and if you place your homepage link on your comment maybe they will click it and go to your blog. So i think with brand your comment on others blog, it will increase your traffic. So Happy Commenting, but not to SPAM!!

Linking : Usually comment are made by entering details like Name, Email, and your Blog URL. So it helps to link your blog from other blogs.
Use Emoticons :  You canalso use some worthy expression emoticons to make the comment look interactive and attractive.
Be The First To Comment : Tried to be the first on every blog post. The first comment is the best immpression, so the first comment is the best way to increase your traffic
Branding : By commenting frequently in blogs will help others to remember your name and blog name. Even regular readers will be aware of you and your blog. Most popular blog have top commentator widget installed. So always tried to be top commentator of a blog. It effectively inrease your traffic.

As per i consern never/ever spam your comment! Don't misuse or abuse commenting
Source : hellboundbloggers