What's to prevent someone from hijacking my username?
Since usernames are only unique to the instance it's created on, what's to stop someone from creating a copycat username in order to impersonate another user?
I'm sure this will happen. People do get crazy when Internet arguments occur. But what is the risk to you I wonder? If they do something that will get them banned, it will only affect that account. Do others really pay attention to usernames? I don't.. I could see someone coming into a contentious debate and trolling but ultimately do any of these debates really matter outside of just the sharing of knowledge and ideas? I'm trying to think how it could really negatively affect me other than just being rude and offensive to my ego.
I mean depending on how you look at it. Usernames are really your name + instance, and that is unique. To know you are actually talking to the right person you just have to make sure that matches up