always remember high PR site is different with high PR page Even you get a high PR blog, but comment only at zero PR page in that blog, you'll get nearly worthless backlink
For what it's worth, I use linkvault to get on the first page of Google results and it works well. You just got to make sure to grow slow of Google will catch on and penalize your site. DP also has a great program that does the same thing called co-op. Just remember, grow slow!
On the jyse, i type in highlight health. First it ask me authenication required 5 times then when i try to comment it said type the security word in the picture to improve that i am not a bot. I could not find the security word
Commenting is a great way to build backlinks and relationships with other niche webmasters. You have to be careful not to spam your comments, as this is bad netiquette and poor SEO tactics.