I have to admit, I am COMPLETELY clueless as to exactly what this is, so I am going to copy and paste from my friend's site. I just know it is good for my blog, and for all my readers who need to build up their site traffic as well!!
In case you have been wondering what that U Comment, I Follow item is in my sidebar, here's an explanation given by Randa Clay over at Randa Clay Design.
Almost all blog platforms by default are set up so that a “dead end” piece of code is inserted wherever there is a link in a comment, so that search engines will not “count” the link as they are crawling the internet. This was originally designed to help stop comment spam, but it doesn’t work. What it does is remove some of the incentive for your readers contribute to your site by commenting on your posts.
What can you do about it? Turn off “nofollow”. Show your commenters that you appreciate them. Spread the link love.
How? Depending on the blog platform you’re on, you can install a plugin (like this one for WordPress), or disable it (see this post if you’re a Moveable Type user), or modify your template (check this site for Blogger tips).
Turning off the “nofollow” on blog comments has become a sort of “movement”. Well, if we’re going to have a movement, we should have something to show our readers that we’re part of it, don’t you think? I’ve created some little “I Follow” logos that would work well for a side bar, and if you’ve written a post letting your readers know that you’ve turned off nofollow in your comments, you could link the logo to that post.
As an addition to Randa's great tutorial, I just wanted to mention that the whole reason why blog platforms do this to begin with is to prevent comment spam - spammers spamming blogs with spam comments (can I say spam any more in this sentence?) in order to gain links - as long as you have some sort of comment moderation (Captcha letters or owner approval) you won't get spam comments!
And I have to say thanks to MamaBear, because without her help, I would still be in the stone age! I am no good with computer stuff, HTML, or anything like that.