Somewhere on that thread, someone named Rebecca gets told maybe it would be cool if she went by "Reb." This was, in fact, my first handle, short for both my middle name and "rebel" (not the Southern kind, but stemming from an odd occurence in my youth group*). I loved that name, really, even though I haven't thought about it in years. It felt very "me" at the time--maybe still does in some ways--and I wanted badly for my friends to call me by it, but that would be (like Buck) violating the First Law of Nicknames. Plus, self-ascribed nicknames rarely stick.
"Seraph" was thought up for me partly by a friend of mine in highschool (The Mastermind), when I was making my first-ever online journal. I tend to overthink screennames because I want them to convey my identity more fully than a lot of people tend to bother with, and I had trouble thinking up that one because I felt that my social identity was in flux at the time. Mastermind suggested some combination of "shadow" to express that gray area, and "seraph" because I'm religious and it sounded cool. Eventually the shadow part got dropped but Seraph stuck somehow.
In a lot of ways I think of myself more as Reb or Seraph than my real name. But there's no way calling myself by those names in social situations would fly. This comes from very early personal experience, when I tried to get everyone I knew to call me by the name of a candy that I liked, and which sounded vaguely like my name in some contexts. I think only two people ever called me by that name, and one of them arrived at it on his own instead of having me try to tell him.
Maybe names aren't something we're meant to pick for ourselves, somehow?
*One time, my youth group in the course of a Bible study was asked to think up a bunch of people they would call "rebels" to write up on the white board. My name ended up there alongside Che Guevara and Saddam Hussein, probably due to my perpetual tendency to play devil's advocate in discussion rather than immediately swallowing the usual doctrine. Maybe they should have called me "Buck"? The actual point of the exercise was to demonstrate that while most people that youth-groupers will call rebels are "bad," there is a good way to be rebellious, especially since Jesus was portrayed in that study as "The Ultimate Rebel."