Have you ever copied a fan fic or story over to an editable format and made corrections or annotations? I haven't done so with fan fiction but have been tempted to more than once. I have made annotations or comments to actual books though.
I have seen a few good fics that had relatively minor errors that individually could be glossed over (and easily corrected without changing any of the plot or feel of the story) but as they accumulated become annoying. It is not just grammatical and spelling errors but minor things from the actual work. Characters making out of character statements or actions are the most common but I find myself being annoyed by extremely minor details that really shouldn't bug me far too often.
Here are some examples of extremely minor details that recently (as in the last few days) bugged me:
- A character's canon eye color is stated to be one color but the fan fic has the eye color be different. In this case it stood out because the original work made mention of the eye color repeatedly.
- Statement about two characters both being the same age within days when the original story stated clearly that one character is 10 months older than the other.
- A character is shown to always have a clean room is even shown to be upset by a dirty room and compelled to clean the room even if the character has no reason to do so being stated in one single throw away line to always have a messy room.
- A character shown to care about their physical appearance wearing many different (some of which would have been extremely expensive) articles of clothing stated to always wear rags.
- Statement about the ease of an attack or defense (to the point anyone could do it) when the canon story stated and showed that that it is difficult for the majority of people and the ease in which the character was able to do it in the original story was to portray how good that character was.