BTW, why use a throwaway just to make a mildly controversial remark? The internet points aren't real. What's the point of anyone using consistent names at all if we use throwaways whenever we say something interesting?
* People cannot trace which dumb things I talked about in the past to use ad hominem on me. I felt disgusted when attacked by ad hominem. Without chilling effect of being dug from the past, I get more freedom in expressing opinion.
* To stay anonymous in a reasonable way, in the sense of preventing people from profiling username. Reading someone posting as 'anon314' or 'throwaway2021' would feel different from someone as 'hiimelonmusk'. It would leave no remark in the back of one's mind.
The first argument... well I just don't get it. Why do you care so much if some internet weirdos are looking through your history in order to win internet battles? Care about what you want, but it doesn't seem very healthy.