Traitor

"Within the year he ended the old feud. giving up half of the disputed lands to Domain of Stok. For this and for the murder of his hearthbrothers, he was called Estraven the Traitor."

In chapter 9, after hearing the story and the conclusion of the story ending in Estraven gaining the epithet of "the Traitor," It really brings into question the meaning of traitor. In this case, Estraven did betray his kin and arguably surrendered his clan to another but one can hardly call him a traitor for it. If anything, I'd call him a hero for it since the continuance of the war would've brought much more pain and suffering to his clan. Similarly, the young Estraven faced a similar situation since he was exiled for supporting Genly but was probably actually exiled for his opinion on the Sinoth Valley. Estraven wished to avoid war with the Orgota but Tibe probably got the king to exile him because he was an obstacle in his plans which we shall probably see unfold later on.
Anyhow, I believe that the meaning of traitor will probably become even more important as the story continues. In my opinion, you can only be a traitor if you betray yourself. If you are forced to act or think one way and you later show your true opinion you can hardly be called a traitor. If anything, it is more traitorous to supress your true beliefs and perpetuate some phony facade because when it really comes down to it, you won't be able to keep the facade up forever and then you will truly become a traitor.