I don't support playing out sex scenes with writers who are in a different life stage as you if either is not 21.
Examples of what is okay for me:
M!15, with F!13.
Teenage boy, teenage girl.
M!18, with M!23.
Legal teen, young adult.
F!29, with F!38.
Adult, mature adult.
M!19, with F!40.
Legal teen, mature adult.
Examples of what is NOT okay for me:
M!18, with F!13.
Legal teen, young teen.
M!16, with M!20.
Mid teen, young adult.
F!14, with F!23.
Young teen, adult.
M!10, with F!17.
Prepubescent, older teen.
... In short, sexy times with a minor is just squick-able.
Some people will probably argue that some teenagers are mature enough to: (1) write as well if not better than some adults, (2) differentiate between fiction and reality.
Yeah, no. Sex is most of the times part of romance, I do agree and believe, but 90% of them do not require explicity in a story.
I personally encourage teens to explore their sexuality as long as it's within moral boundaries. Paedophilia and hebephilia are not fine. Besides, it just creeps me out to imagine someone a chunk few years my junior writing out a sexy post to me.
Granted, people lie about their ages. Can't be helped in such cases. But those who knowingly engage in erotica with a minor are questionable - detestable, even.
More often that not, these minors are confused and afflicted with the ever-present loneliness teens feel amongst their own peers. And predators of these folks usually try to break down barriers by smutting "strictly in character", then being affectionate OoC ...
... and then they try to coax you into sending nudes. And probably will blackmail you with said nudes.
Most, not all, minors just don't make the best decisions. Those as adults should know better than frolick in curious indulgence with them!
(Oh Lord. Am I slapping this into the wrong thread? Unpopular opinions, right? Is this still considered a roleplay topic, or a debate of morals?)