unpopular(?) opinion: it annoys the hell out of me when people tag fic about siblings or other family members with stuff like "this isn't incest fuck you if you ship it romantically" or whatever
like buddy. I KNOW it isn't incest. I didn't think it was incest, I wasn't thinking about incest at all in fact, and I would really have liked to have CONTINUED not thinking about incest except every damn author in the tag feels the need to remind me about it constantly. people who do this shove incest ships into my face way more than actual incest shippers do because they won't fucking stop talking about how much they don't ship incest.
please just tag your fic with the things it DOES contain and don't worry about the things it DOESN'T, okay. I promise you no one's gonna think your fic is full of secret incest even if you don't spend 30 minutes decrying it in the tags before every fic.
In a similar vein, I avoid reading things tagged No Underage Sex. The vast majority of the things I read does not contain underage sex, but if an author is so afraid of the concept that someone might think they would write underage sex that they feel the need to tag for its absence, they're too anxious about it for my taste.
My avoidance is only reinforced by the fact that in my circles, "No Underage Sex" is occasionally code for "No one admits they want each other till the younger party is 18 years and 1 second old," which is what you get when people are squicked by underage lust, but not by age gaps. Pretending that there's no attraction before the object of affection is 18.0000001 is perfectly valid as a kink and diametrically opposed to many of my kinks, which involve people owning their kinks.
Now I'm wondering how often people write "Relatives, e. g. Dean and Sam Winchester, discover that they're not biologically related which makes it okay for them to bone down, so they do, despite having believed that they shared genes until the Ancestry.com test came back," which seems similar in disingenous-to-me effect.
Write what you want to write. Tag appropriately so that people who want it can find it and people who don't want it can give it a pass. Accept that the vast majority of the people in the fandom, let alone the world, aren't going to read it no matter how good it is.
I've seen this same thing with art posted on Tumblr. People will be like, "this is PLATONIC so don't be a freak and tag it as a ship" or whatever and I'm just like. Babe. Sweet summer child. You can NEVER control how anyone else interprets any kind of art. And you put that on the internet, so now it's completely out of your hands. That image or fic or gifset will mean whatever other people want it to mean in their heads and you just have to accept that.
And honestly, I think that's one of the coolest things about art - every work becomes something new for every person who experiences it.