- Victory is not automatically honorable. Or, the ends do not automatically justify the means. Unlike Duras and his conspirators, Worf refuses to consider any convenient shortcuts to power that would compromise a code of honor.
- Mercy and justice are as important as strength. Worf doesn't kill Toral, son of Duras, for the sake of revenge.
- Unity and harmony are worth the cost of any one individual. Worf accepts a label of dishonor for the sake of at least temporarily averting a civil war. I suppose it isn't as poetic as the quote about the "needs of the many outnumber the needs of the few...or the one", but I think choosing to live with dishonor is in fact a much greater sacrifice than death for a Klingon.
- Personal moral satisfaction matters more than societal acceptance. By stating that there is a difference between the "Klingon way" and "my way", Worf demonstrates a mature stage of moral development in which he makes his own decisions. One of the harder concepts for me was the idea that someone has to earn honor from others. I understand not wanting to disappoint your mentors, but it seems like complete horsepucky to jump through hoops just so other people will admit what you know about yourself already.
- The greatest loyalty to a specific entity will sometimes be expressed as discontentment with its current state. Worf steadfastly refuses to support a Klingon invasion of Cardassia, but he is no traitor. If he didn't care about the Empire at all, he would let it do whatever. If he followed the Empire just because it was the Empire, he would still let it do whatever, and also participate. His dissent proves that he believes in the Empire as an ideal which the real Empire should strive for.
- Different moralities can learn from one another. Picard says that Worf has taken the best of humanity and used it to become an excellent officer. Someone who is too insecure to approach a different morality without bias also is closed off from learning the best of what that morality offers.
These moral lessons are not unique to Worf. Worf is an instance of a prototypical "honorable warrior" character (maybe originating in the samurai or Beowulf?) whose battlefield honor fuses with an understanding of love, until the warrior learns to avoid war unless necessary to protect the good. I think I read once that a beginning warrior has a weapon in his hand, an intermediate warrior is one with his weapon, and an advanced warrior carries no weapon at all. Dinobot in Beast Wars Transformers is another good example. Don't believe me? Read this, which explains the concept better than I ever will.