Planet13 - 4:04 pm on Aug 24, 2013 (gmt 0)
"It can't help for better ranking but definitely it can drop your ranking if doing with bad way."
I would disagree somewhat.
I would say that in some instances, it CAN help quite well for ranking purposes - if done correctly.
But it would appear in my experience that it can lead to problems later on.
The secret is knowing exactly which sites to comment on - and no, I ain't telling ;)
The problem is, those links will almost certainly become Penguin fodder eventually.