If a user group does not have permissions for links in there signature, they can still have the (non-clickable) URL as text. i.e. the text is there, but it does not act as a hyperlink if you click on it. This is the way it always was I believe. The problem is that if the forum has Convert URLs to Page Titles enabled, then this text (which is not actually a link) is still converted to the page title as if it is an active link. I can't believe this is by design so I'm posting it here.