I’ve been thinking about this a lot, and come to the conclusion that it’s not the characters who have preferences about this, or anything else to do with sex, it’s us. And that’s OK.
Sometimes you see a character and your id’s all “wow, I would so love for him to get a good, hard fucking” and why the hell not? Create, curate, and consume all the fanworks about your fave getting his arse pounded. Someone else’s id might look at the exact same character and reckon they should be dishing out a dicking rather than receiving one, and they are every bit as entitled to their own pursuit of happiness. It’s a big internet, the porn rations aren’t about to run out.
Preferred sexual positions are not a reflection on personality, appearance or, saints preserve us, ethics. It’s just about what’s hot. Sometimes you’ll see a character and just know that she needs to sit on all the faces, but let’s not pretend that’s some intellectual deduction. Sometimes you want a character to be stuffed with dicks and it’s fuck-all to do with their height (unless you have a height kink of your own, of course). And switching for spicy fun is great, but has fuck-all to do with equality.
You can’t tell how sensitive someone’s prostate, or clit, or nips are by the way they relate to family members in canon, y’know? There’s no objective truth about how someone’s height, or their character arc, how assertive or loud or shy they are, their age, favourite food, or how they dress that determines their sexual preferences, and it’s only when we pretend that it does that things start to get icky.
It’s totally cool to have preferences about characters you like to see top or bottom, sub or dom, switch or abstain, or whatever, but let’s all just own our own preferences and not pretend they are anything more than that.