I answer to whatever I'm called on forums I've been Joycy on a few and Di or Para on a few and none are the true 'handle' which is a little unusual down here and somewhat more easily traceable for hackers, and me being so paranoid and all.... well you know how it goes.

I Googled it once and there's only one person with exactly the same first and surname on there and she's in the States. I'm still off the Google radar.
I only ever use it on official forms and it was never used by anyone other than in official capacity. I was called different things by different people as a kid and it's never bothered me, they can call me as they see me. It was usually roughly based on the original but never the 'official' handle.
The first argument I ever had with 'officialdom' was telling my first teacher on my first day at school that she had my name wrong. I had never been told, and had never heard spoken my 'real' name. I literally didn't know who I was! How embarrassing, what a great start to school life.
No one ever called me by it except at roll call anyway, and eventually the shorter version was used there too.
I find I address people based on their usernames, I figure if they expect their real names to be bandied about they'd include it as a username but that's just my convoluted thinking. I don't use their real names usually, even if they've mentioned it on public forums As I said, if they wanted it known to the World.....
