User blog comment:Seishoujo/Fanons are disturbing/@comment-10380701-20131006071418/@comment-4010415-20131006091507

I can imagine. I was mainly talking about the brony community as the other fandom. As soon as people see an alicorn OC, they jump on it like "OP! Bad OC!" Though, one of the issues is that there isn't supposed to be some abundance of alicorns.

People are against black-and-red OCs because the pattern pretty much shows that black-and-red ponies are often bad OCs. Same with recolors.

Tragic/grimdark back stories because, well, duh, it's the frickin MLP universe. Why is your OC an abused orphan blablablah?

And in any fandom, it's kind of inappropriate to make your OC have some big relationship with a canon character, like "I'm the main character's sister" or something.

Once you learn the patterns fandom-wide and within-fandom and keep the canon in mind, I guess it can be pretty easy to detect a bad OC.