Great question Eugene, and one that we spent a lot of time discussing in our offices when we were designing our forums.
Our team worked very hard to put an emphasis on conversations, debates, and ease of use. From our experience, we found that signatures were clunky, and got in the way for reading through a thread.
As such, our team decided to spend time on people's profile pages, allowing them to add a "tag line", as well as links to your website, and information about yourself. Simply click on anyone's name/avatar, and you will get to learn all about them! We will be continuing to better the profile pages.
I hope this helps, and we look forward to hearing if anyone else would like to see signatures, and/or their thoughts on the above.