When I was in university, a friend of mine used to address me by my unix username.
You got off light. I had a good number of people call me by my username at my undergrad.
When I went to grad school, they let us select user ids. My user name matched my first name, most elegant solution to that problem yet ;)
There are several people I know primarily through wechat, where it's almost always unnecessary to address people by name because messages have only one recipient. Sometimes this has led to conversations like this:
> What should I call you? 颖？
> OK.
[I was not especially reassured by that response.]
Heh, there are still some people who call me by my nickname back from 2000s. It doesn't help what it means something between "the beast" and "the thing" and I had people of the old clout be quite offended by it. Including my mother.