This subject caused some very serious and heated debate on another forum I use sometimes, with some users objecting to the anonymity of of usernames and adovcating that everyone should post under their full name (as some on that forum do). Others replied with various points that have already made and others (for example, suppose I registered as "Katherine Sutherland". That looks like I'm posting under my real name, but it is not my name, nor is it even closely related to my real name.)
I use fimm a lot on various forums. It is kind of related to my initials. I like usernames. I'm often intrigued by other people's usernames. Where did dellzeqq come from, for example?