Hey, Davros.
I had noticed this, too and was wondering the same thing. After reading your post, I got to thinking (something I'm not accustomed to) and I figured it out.
You only have to do this on your sig, not in your post. In your post you just type it out like you always did, or at least it works for me that way. In your sig, put the URL in brackets, like when you post a pic. [url ] url [ /url] with no spaces.
I hope this makes sense.