I just typed a reply telling you that it is impossible to do this, and to check my signature to find a plain text URL.
To my own surprise, i saw that that link actually is a clickable link now.
Come to think of it, i do think i did some test on this a while back.
I don't know when that has changed.
I did change it to text and decided to keep as is when these measures were taken.
I still think it should be like that and not some other text containing a link, so people can see what they are clicking (although you would expect that anyone here wouldn't just click any link without seeing where it will take you).