Language
In a lot of movies with non-English languages, they either keep it in the language and use subs or do a transition like in Hunt for Red October where the audience then assumes when hearing English that they are really speaking Russian (or Klingon in this case). Ergo, I was a little confused by the Klingons continually mixing English and their language. I assume they were meant to have always been speaking their own language as it wouldn't make much sense to use a human language (except when conversing with Kirk).
Just struck me as weird.