Anyway, here's a quick question to those who know: Swearing. In particular, swearing in fanfic. I've never done this before, since my characters tend to use the sort of language they use in their source material, but one of my outsider viewpoint characters in my current story would really like to be able to pepper his scenes with the F word. What rating does such a thing require? Is this an automatic R rating, or can such things pass nowadays in a PG-13?
I find rating really hard. The fact that the custom is to use American movie ratings (different from UK ones) is only a small part of the problem. It's all just so subjective. One person might not bat an eyelid at something that someone else finds really disturbing and definitely not for children. I've heard passionate debates at children's librarian conferences, when one librarian considers a book fine for ten year olds, and other thinks it should only be for older teenagers. I've read furious reviews of books and TV shows that consider them adult-only for some reason that I've not even noticed. (Often swearing, to be honest, which I find odd, since I don't swear in real life at all, so you'd think such things would jump out at me, but apparently they don't.)
It also seems to change over time. I've noticed things happening in PG-rated stories that I think wouldn't have got through 12 years ago, when I started in fanfic. I remember quite a lot of stories being rated NC-17 for violence back then, but containing nothing any more extreme than you'd find nowadays in stories rated a lot lower.
It's culturally specific, too. American TV shows showed over here are frequently edited for violence. Things that American network TV passes as fine for evening viewing are often deemed totally inappropriate by the regulators over here. (Buffy was frequently marred by the censors, and Angel totally butchered.) However, British TV is more accepting of sexual references and swearing.
And then you've got the issue of general darkness or disturbing subject matter. It's so much more complex that counting the gouts of blood and quantifying the flashes of flesh. These things make it easy, but you can have a story with no sex, no violence, no swearing, no drug use... yet still have content that most people would consider unsuitable for children. It's almost enough to make me wish I wrote sex scenes, so I could slap an NC-17 rating on everything and be done with it. Trying to wrestle through the PGs and the PG-13s and the K+s and the Ts is just so hard.