I agree with @Mikl on this one. Google is smart enough to know that a comment link is just you commenting on someone else's article. Google would much rather promote the sites that produce content rather than the ones who simply comment on it.
If you want good backlinks, you should contact a lot of people within your niche and write content specifically for their site in exchange for a link. This takes a long time and it is hard work, but 5 of these links are more valuable than 50,000 blog comments, forum sig/profile links, social bookmarks, link wheels, etc.
In reference to your questions about keywords:
The keyword research should determine the Title Tags and META Descriptions for your pages, and it should determine the TOPIC of your articles and the ones you promote on other people's sites. I like to put 1 long-tail keyword in the title of all of my blog posts. Don't worry as much about anchor text in the guest post article or anything like that. You are much better off just using the name of the site or your name than having keyword specific anchor text for every link.
You should go into this like you are trying to become the foremost authority in the industry on Louboutin shoes, not like you are just trying to rank for certain keywords. Google can detect patterns when people try to exploit their algorithm to rank for certain keywords.
The people at Google are pretty sharp guys, don't underestimate their ability to do anything.