I hated warnings on fic at first. I didn't want them as a reader, and as a writer I didn't want to tip my hand to my readers. I didn't even want to state pairings for some stories, because, well, what if I wanted the events to be surprising? This was my first clue that I was being a bit silly, because I'm as pairing-focused as anybody when choosing which fic to read. I'd probably be grumpy if a fic I thought was headed in the direction of OTP Bert/Ernie suffered a sudden twist and ended up as disliked Big Bird/Ernie. Then I realized that in addition, I didn't particularly want to read Bert and Ernie performing certain kinds of sexual acts. Not only did I want the pairing indicator, I also learned to appreciate warnings.
Later, while contemplating a warning for hurt/comfort on a story, I had a minor insight that most of you have no doubt shared. "Warning" is the wrong word, most of the time, for what is a story content label. Was that a warning for h/c? Only if you hate h/c. Otherwise, it's a happy indication of desirable content.
Story headers aren't about spoiling the content; they're about reader strategies.
"Do I want to read this story?" we ask. The header, if it's doing its job, answers the question. What's the fandom? Who wrote it? Which characters are featured? What's the general tone: fluffy, gritty, action-laden, angsty, unremittingly dark, with major character death? If it depicts sex, how explicitly and what sort of sex?
Once I understood that, I was reconciled with the fandom habit of warnings. In fact, I try to think of the content labels as "tags" instead of "warnings". A value-neutral term fits their use within fandom better. The oft-given example is of kink fic, where the tag "bdsm" would be a warning for some readers and an advertisement for others. It's a content descriptor. Content descriptors help the reader find stories that are interesting, and avoid stories that aren't.
What's my function as a fan writer? What am I here to do? My function here is to be an entertainer, and making it easy to match up readers with fic they'd like can only help me do that. My deathless prose can stand up under the burden of being tagged and categorized. And if I'm clever, I can assign the labels without compromising the emotional impact I want the stories to have on my readers. You can find the stories you crave; I can find the readers I crave. Everybody wins.
Let's return to the current thrash about warnings for trigger issues. Trigger issues, as several brave posters have made clear, are not the same as fic preferences. I can choose casually between this hurt/comfort flu fic and that angsty mpreg epic. Somebody with a trigger issue might need to know that the mpreg angst comes from an incident of sexual violence, and need to know with an urgency that I can't really imagine. I can read the first page of each story and bail if I'm not in the mood for it. The person who's triggered doesn't have the luxury of choice. By the time they realize the fic contains something problematic, it's too late.
I think of myself as the sort of writer whose stories don't really "need" warnings, because I don't go into the sort of gritty territory that lots of other writers do. I am not likely to write what fandom whitewashes as "non-con" as entertainment. Aren't labels enough? Well, possibly, if I remember that sometimes, a content label really is a warning and not just a tag. If, say, I were to write about the aftermath of the violence that occurs in my fandom's canon (say, "Becoming" part 2), then guess what! I'm right in that triggery territory.
I think the peanut allergy analogy works well here, though I realize it was originally proposed by a writer hostile to the idea of warnings. Here's the connection it makes clear to me: There are people walking around with a condition that might cause them grave distress. Their situation is invisible to other people and, sadly, many people don't take it entirely seriously. But they'll have an anaphylactic reaction if they eat something containing peanuts. The burden of self-protection ultimately rests on the person with the allergy, but that burden can be lightened with some considerate behavior from the people around them.
I, as a writer, wish to have a positive, happy, mutually beneficial, and all-round satisfying relationship with my readers. I like you, oh reader, and I want you to have fun. I want you to trust me to take you on an emotional ride. If my story make you cry, or feel tense, or get angry, it'll be because that was the emotional experience you wanted when you started reading. You'll be able to avoid stories that might give you an emotional experience that neither one of us wants you to have. Everybody wins.
Okay. Now that I understand triggers a little bit, I know to put warnings on fic that needs warnings. Warn for what? I keep in mind that most of the trigger-causing scenarios are going to involve the word "assault". Sexual violence, physical violence, direct depictions of abuse, direct discussion of suicide or other self-harm. Warn for those, and I'm 90% of the way there.
The problem is that I, as a fic writer, cannot possibly predict everything that might trigger someone. Does this mean I give up on warnings? No. It just means that both writers and readers need to know the system isn't perfect.
If you as a reader have a surprising or strong triggering issue, I suggest to you that it's wise to behave as if every fic might contain peanuts. If you trust the labels-- because of experience with the writer, perhaps-- then read with confidence. If the labels are absent or untrustworthy, find a strategy for discovering the content. A trusted friend who can read in advance for you, perhaps. Or ask the writer.
From my end as a writer, I will attempt to be considerate and tag my stories with content labels that cover what I know to be the major pain points. My goal is to be a trustworthy labeler. I will change my current habits to add "warnings: none" to fics that don't need warnings, to set expectations properly. When in doubt, ask me. I promise to answer honestly and sans snark. If I discover that a regular reader wants to know about something specific in advance, I'm happy to warn for that consistently.
One strategy I've seen that I respect is a note on every story posted that the writer only warns for two things, followed by a warning or a note that no warning is needed for that specific story. The reader then knows what's covered, what's not, and expectations are set and met by both sides. This goes a long way toward solving the problem, because I think unhappiness lies where the expectation mismatches are. Whatever strategy you choose, if you focus on setting reader expectations properly you're likely to avoid hurting people by accident.