In real life you can maintain pseudymity by just never exposing your identity. This happens all the time, much more often than the Internet (e.g. As I type this under a tree by the road of my uni, no one knows who I am and yet my nick here absolutely identifies me).
Because you are being so open about it why do you feel you need to use a nick in real-life?
A lot conversations for this story seem to have focused on the concept of permanence with a nickname. If you use the same nickname across a multitude of services then you've created a "real" identity.
I'm trying to understand peoples reasoning for this. To me there seems to be two prevalent reasons:
1) You want your single identity to be under a name you choose, not have it be forced upon you like you real name was.
2) You want to maintain a multitude of identities each with a specific purpose.
