Maybe. As I was telling Tracy the other day, I've never been a huge fan of AUs because when I read fanfic, I like for the the guys to be "The Backstreet Boys." I have read really good AUs in which the characters were SO well-written that it didn't matter that they weren't a boyband, but I've also skipped over plenty of AUs because I just couldn't suspend my belief and get past the whole BSB thing.
That makes me feel kinda good since one of the stories you like that I've written is AU lol
Looking back at Mare's little list... plagiarizing myself - HOLY. I wrote a scene with an argument once and it just came so naturally, flowed so well... because I had already written a nearly identical scene in a previous story and ripped off my own dialogue LOL
I guess another faux pas that I am guilty of is suddenly (randomly) spewing really technical jargon based on research I was doing for the story. Took me a while back in the day to figure out how to rewrite things in my own words, especially when I don't really understand it.