Why did you become Red?
Short answer is that Red is an easier shorthand then Vulnus.
Long answer is that I got tired of having people purposefully mispronounce Vulnus to annoy me and after playing Project Reality as RedVulnus I found Red a good shorthand since you could just shout 'Red watch X' over voip so I'd hear that instead of 'Vul-Vil? Whatever the fuck your name is watch X'. Evidently Vulnus sounds like Vilnis to a lot of people.
Do you have an absurd accent or something that would lead them to think this?
I don't know, I'm from Texas so that's possible, but more often then not it happens when I'm not talking in game, either because of my current situation with my mic being broken or when I'm in an outside voip like Discord with people.