I am currently rereading the entire series again and I am Towers of Midnight. I think Mat changed a lot, and Matt seemed to become dumber, I don't think he would spell things wrong, the letter he wrote in Lord of Chaos/Crown of Swords, (I can't remember which right now) its said that he his letters are undeveloped but never mention misspellings. Also the fact that never cared about writing or reading and all of sudden he wants to start writing and making up backstories for people? Seems out of the blue. The way he acts and assumes his smiles can break hearts? I am pretty sure he knows or says that he isn't that good looking, especially when he was unsure why Tylin had him as a pretty. The first time I read through the Sanderson written ones I didn't like them as much and as I am rereading them, they aren't as bad, Matt is still a problem.
As a side note, did anyone else notice that people are using words that they wouldn't know, or "Randlanders" wouldn't have in their vocabulary, like the word slave and devil.