You're self aware enough to realize that there's "some undercurrent stuff", but not self aware enough to pick any other username than F0UKYOU-HN, which just maybe might prejudice users and moderators against you. It's like wandering into a bank with a hoodie, face mask, and a gun, and wondering why security is all up in your grill about a "mysterious" something. You're being profiled at the very start by something you set for yourself. If someone comes into your house and the first thing out of their mouth is "f0uk you!", would you really be inclined to sit down and listen to them and have a thoughtful conversation, or are you going to kick them out at the first sign of trouble? At the very least, you're going to keep a close eye on them, yeah?
In meat space, you can do things to change your appearance somewhat, but people gonna people and they're gonna judge you, some times fairly; sometimes not. Online, the only thing people have to go off here is your words, and choosing F0UKYOU-HN belies a certain amount of aggression that is naturally going to start people off on the wrong foot. How do you want people to see you? You could have chosen anything, maybe something bland or generic, like mikelovesbikes32, but in choosing what you chose, you wanted to make a statement, and with your statement, you're "baffled" by why the human being on the other side of the screen might take offense?
