It doesn't matter about the fact if the person is nice or not. After all, outside the internet, except my parents, my brother and a selective amount of girls, no one calls me with my real name either. Though 'Ed' or 'Eddy', usually does the trick well, and I respond to 'Edwin' as well.
But on the internet, it remains Fladian for everyone. Flad for friends, Fladina for the drunk but Fladian it is. Fladiano, Fladiany or any of those just don't sound right or I am not fond of them. But usually, it's the first. Unless I am very fond on the person who calls me that, I'll mention it.