I'm reading an author's rough draft, and I know there have to be some mistakes, all rough drafts have them, but oh my gosh, the punctuation.
This is why I hate editing someone else's. I'm a grammar… er, perfectionist, and I always make so many corrections on my friends' papers. Their papers are basically just all pink when I'm done with them. And then that convinces them that they're awful at English (which is true for some of them).