I'm usually able to tell the difference between canon and fanon, but there are times when stories change my opinion.
Silent Ponyville and Psychology series: Just because it is all rainbows and butterflies on the outside doesn't mean Equestria is perfect. They still have darness, monsters, nightmares, horrors, and possibly crime. Yet each character has had to overcome hardships of their own. This makes them stronger, more relatable characters.
Fallout Equestria: Ponies aren't perfect. Just because we haven't seen a war doesn't mean they haven't happened (besides Nightmare Moon). They have the same failings we do.
Conversion Bureau stories: Although ponies have their faults, they try harder to make the world(s) a better place, and the honestly respect and care about others.
Derpy: I don't see her as a pony who drops pianos and breaks town hall. I see her as a kind, honest, hardworking pony, possibly a single mother. She has many hardships in her life, yet she won't let her handicaps or the opinions of others defeat her. Some of my favorite versions are
Today, Tomorrow, Forever: Single mother struggling to raise her daughter. Gives her up to give her a better life.
Words are Louder and Blood is Thicker: Genius with a handicap. Adopts a poor orphaned filly. Some are prejudiced against her and take Dinky away. Does everything she can to get her back and prove herself worthy.
Ditzy Doo: Muffins: She has a fierce, dark side that she keeps hidden. She will do anything to protect those she loves. She has a forgotten past that returns, revealing where she came from, how she came to raise Dinky, and what her cutie mark really means.
These are just a few examples. I still prefer fanon Luna to canon Luna.