Blog commenting was never meant to be a link building method bro, it's just a normal way of letting the blog owner know who you are, just like you mention your name and email address. But we often use this as a way to generate backlinks. :\ It's okay, as long as it is natural... if you are reading a blog post about food, say Biriyani and if you liked that post, and want to know more about it, so it's cool to comment there using your blog link and so. But you shouldn't repeat this thing again and again just to build backlinks. That is suspicious and might affect you later.
Nah, they have money bro, they'll do all the possible ways to get authority and organic ranking.