Is there any way I can change my username?

I'm sorry there isn't. You're not the only one who hates your 用户名 though, at least Jeffersonian is simple to remember and can be shortened to Jeff which is kind of cute (wait no, *sobs* Jeff Goldblum ruined my 最喜爱的 显示 so I hate the name Jeff), try to find some positive things about your name eventhough 你 don't like it anymore. Oh and don't rant like me, you're supposed to find that oddly placed 评论 funny (It's probably not though) so you'll forget about how much 你 dislike your username.