I've been using this username for stuff since seventh grade (that's about 10 years ago). I, for whatever reason, thought it was a really funny screenname. Now, I use it because I enjoy the occasional 'You lived up to your name with that post" remark I've heard a thousand times.
So there's no real meaning to the dumb or the 180 bit. Just something I picked.
Link and I. Pretty simple, the phrase came from my boyfriend calling me from another room "What are you doing?" my reply is usually something along the lines " Link and I are....(insert whatever it is I'm doing, usually killing bad guys!)".
Well my name in real life is Xindi (pronounced Cindy) and of all my friends I was the only person without a nickname. Then one of my friends suggested Xinnamin (pronounced Cinnamon) as a joke. It never stuck in real life, but I decided I really liked it as a username and now I use it for just about everything.
At this point, it's simply habit. I've had this username on AIM for 5+ years now, and re-used it on several forums.
But my original reason was a cultural commentary on the Internet at the time I posted.
Basically, the Internet was dominated by a lot of intellectuals at the time, often having these drawn-out philosophical arguments in styles that remind you of ancient Greek or Renaissance philosophers. Usually they had these imposing names like "Socrates," "UltraNerd," "MindMaster," "ZeusDeus," or something like that. I just called myself "athenian200" as a way of saying that I didn't think my thoughts were anything special, or amazingly logically consistent. I'm just a "regular athenian" existing among all these arrogant Greek intellectual gods, occasionally tossing my two cents into their debates, but not bothering to defend my opinions, and simply agreeing to disagree with anyone who tosses out an opposing remark.
The name doesn't make much since now, because these days there are a lot of regular people on the Internet, and those intellectuals rubbed off on me to the point that I'm now, ironically, one of the geekier intellectual types in the average group I encounter.
Also, there's not a lot of respect for my desire to avoid confrontation these days, and no matter how much I emphasize that I respect the other person's opinion, they just keep tearing into me and trying to force me to agree with them. Even calling me stupid, because I happened to say something contrary to what they believed. Sometimes I even get so frustrated with that attitude that find myself using the tactics I learned watching those old arrogant geeks defend their arguments, and end up looking like an arrogant person myself. Even though I'm not at all confident in my opinions, I still get annoyed at seeing them dismissed with no justification (or even false information).