Ian - Welcome to WMW. We find it simply works better to draw the line at 'no sigs' rather than try to define what makes an acceptable signature and what doesn't. You can put any pertinant data you like in your profile and users will look there for your URL etc.
Thanks for understanding and having the courtesy and forethought to ask. :)
<added>I see mivox beat me to it. Maybe I just type to slow :)