To use your facebook profile picture as a smiley on chat or comment what you need just your profile id. Open your Facebook profile , you will see a link or URL on address bar of your browser like this http://www.facebook.com/profileid where profileid is your facebook profile id. Like my facebook profile id “anzaq.ali”.
Now when you need to use your profile photo as smiley just type [[anzaq.ali]] in chat. It will not work if you don’t use two square brackets.
Now use anyone’s profile pic as smiley on facebook chat, you just need profile id.