Does Blog commenting works for SEO?

[kanagaseo]

I see blog comments as traffic generating technique, not really a SEO technique, because:
Most blog owners use Nofollow for external link. Especially, the quality sites that have good engaging traffic, never give dofollow links
It is really tough to get good (desired) SEO link juice to your site since well-formed comment to benefit your site is never approved
To get most out of comments, you really need unique contents. It becomes tough when you try to do that for each blog

But, I'd not call it a waste of time, because it has good potential to bring traffic to your site. Many sites that engages your target audience, you should be active on those sites. And the best way to ensure that is through blog commenting.