The code no one actually has
For most of us, morality isn't something we sit down and think about extensively. You're told at a young age that it's wrong to hit people, it's wrong to steal, it's wrong to set Mrs. Henderson's front lawn on fire and then claim that the dog did it. As a result, you develop your morals mostly through experience and occasional moral outrage, often winding up with several moral exemptions that you don't really think about. (It's not all right for your spouse to flirt with someone else, but it's totally all right that you made out with someone else at a party because you were tipsy.)
The temptation when thinking about character morality is to set up a codified set of behavior, but the problem is that no one actually has these moral codes. The closest you get are characters meant to be part of a religious or spiritual order, and even there you'll find some nudging of the edges of any given code. Yes, you dedicated your life to a deity who tells you not to kill, but there's nothing in there about maiming.
Your character's morals likely will consist of a few hard-and-fast rules, a few loose ones, and a lot of gray areas that he or she decides mostly through instinct and situation, unless your character happens to be particularly introspective or possibly a philosophy student.
All right, so your character's moral code is more accurately a few moral rules and a lot of wiggle room. There are still some obvious targets to hit and things that your character will likely have a strong opinion about. These aren't issues that your character must care about, but they're quite likely.
Killing: Odds are that your character is fine with killing under the right circumstances, since most MMOs require you to occasionally throw a rock at something. But it's the circumstances that matter. Will your character stab someone in the back? Kill an unarmed opponent? Kill another sapient being? There's a lot of wiggle room in here for permutations; your character could be fine with attacking someone from behind (it's easier, after all) but not with killing an unarmed opponent. Should all fights be fair, or should all fights be won even if that means being unfair?
Stealing: Pretty much everyone agrees that stealing is wrong, since none of us likes to have his stuff stolen. So this is more about arguing exactly what qualifies as "stealing." If I take something from you but you have so many other things you won't notice the loss, is it stealing? If I have no other options but theft, is it stealing? Is it right to steal something back that's rightfully yours? If you don't make it hard enough to prevent me from stealing it, do I have a right to take it?
Honesty: Is lying acceptable at times or under certain circumstances? Do you owe it to anyone to tell the truth, even if it might hurt? How strict is your definition of a lie? Does it include lies of omission or deceptive wording? Most people like to think of themselves as honest to some degree, but we all will occasionally block out the truth one way or another.
The letter and the spirit
One of my long-running characters is not generally seen as trustworthy, but she isn't a liar. This is important to her. She absolutely never lies, assuming you define a lie as a statement that is explicitly false. That does not mean that she tells the truth, and she has in fact made a longstanding habit of stretching the truth as far as it can go before she winds up on the side of falsehood, but she still hasn't lied.
This is a moral belief of hers. But she's following the letter of "don't lie" rather than the spirit. You could argue that not lying includes not saying things that imply something other than the truth, but that's part of the trick.
You won't kill a man in cold blood, but you might set fire to his house and not warn him. You won't steal money from your friends, but you might borrow some and "forget" to pay it back. You won't cheat on your partner, but what you did technically wasn't cheating. We all build these little exemptions into our morality, ways to stretch what we see as right or wrong into what we want to be right or wrong.
Your characters will have these as well. Sometimes, it's something the character knows about and is fine with -- my honest liar above knows full well that she's stretching the definition, but it's intentional, and she wouldn't take anyone else to task for doing the same. Other times, it's caused by a disconnect between what your character thinks he believes and what he really believes. It's the sort of thing that can lead to character growth over time, the realization that your real morality isn't what you thought it was.
Moral codes can change as we come upon new information and gain new perspective. More than that, they should change over time. That's one of the central parts of character development -- realizing that you were wrong before and changing your beliefs to account for your previous errors.
Of course, sometimes you realize that before you were wrong about not slaughtering those who disagree with you. Not all character development is improvement.
I'm not going to say it would be wrong if you didn't leave comments below or mail your thoughts to firstname.lastname@example.org, but it certainly does make me happy when you do so. Next week, we'll undertake a different profession discussion than I had previously planned focusing on the creative side of life. The week after that, let's look at community drama and how to minimize it.
Every Friday, Eliot Lefebvre fills a column up with excellent advice on investing money, writing award-winning novels, and being elected to public office. Then he removes all of that, and you're left with Storyboard, which focuses on roleplaying in MMOs. It won't help you get elected, but it will help you pretend you did.