1. Incest. Especially between siblings. It's disgusting and uncalled for; it's also breaking the law!

2. Rude Potterheads. People can be so rude sometimes just because people have different opinions on ships. Can't Potterheads work together to make better fanfiction and better theories? Can't Potterheads just work with each other instead of against each other? Lord!

3. Your and you're. Your is you in possessive form. You're is the contraction for you are. My grammar lessons for the day, people!