Found it,but in order to use it,you need to know the right number.I think when you go to your profile there should be a special number in the URL it self that you add to the end of this link.Other than that I can't help you.
What would my URL be? I have no comments, so I can't check. I guess another way is to get another user to mouse over the add friend button on you, and have them write down the number.
Here's how I did it. I logged out of this account, and logged into my other one(Asparagus). Then I went to my user page. I right-clicked the "Add Friend" button, and selected "Copy Link Location". I then logged into my Hellian00 account, and pasted the link into my address bar.