everybody who has already posted is right; however, markdown parsers stop parsing markdown when it's contained in an html element! you have your link (in your bio) contained in a <center> element, which means that the parser isn't parsing anything in there as markdown (which sometimes doesn't happen... randomly)

anywho, tl;dr, you can just use html if you'd like: <a href="abcd">abcd</a> like this!