Author's Notes (often called ANs or A/Ns) often take up the head and feet of a fanfic, either for every chapter or for the whole of the story. While they can occur in goodfic, they are more infamous for their annoyingly frequent appearance in badfic.
Especially irritating Author's Notes may be counted as a charge. This is often the case if they are in-text Author's Notes, like this:
And then Legolas said, "Oh yes, you're so beautiful." Then he kissed her. (AN-Orli is so hot!!!)
Author's Notes, as experienced by agents inside a fic, tend to be disembodied voices echoing inside one's head. Especially bad Author's Notes can be ear-splittingly loud, and tend to induce a matching splitting headache in anyone unlucky enough not to have covered his or her ears. Agents have even been known to pass out entirely.
Particularly bad Author's Notes have sometimes become physical disruptions within badfics, which can lead to some... unfortunate situations if an agents is caught unawares. Additionally, it isn't unheard of for Author's Notes featuring character interviews (usually conducted by the author) to materialize as really cheesy puppet shows.
If an author's note is properly differentiated from the text, it is more difficult for agents to read than normal Words.