Should never have occurred. Hire an escort if you want to help the kid get off, which is weird enough. Or buy him a flesh light with a mount so he can just fuck it.

If someone made up this story today, it would be his stepmom and no one would care

But also, a bunch of redditors mixed chili with soap so what the fuck do I know

Well, ignoring any veracity of the story, as a hypothetical it has a degree of moral validity. Let me repeat, I'm exploring it as a hypothetical, and won't go into that specific story until the end. So if anyone starts screeching before they've read my wall of text, they can fuck right off.

Incest is a thorny subject because there's a shit ton that can go wrong, and in any realistic sense is going to go wrong. But purely as a hypothetical, if everything went perfect, nobody gets hurt. To me, that makes it none of anyone else's business, and ethically neutral.

But look at that caveat. It's doing a lot of work. Everything going perfect is just so unrealistic. The power dynamic of parent and child, even as adults makes it nigh impossible for there to be less imbalance than between two random adults. And any relationship has some degree of power imbalance because that's the nature of a dynamic human interaction. You can get that balance close to ideal, but even something like a minor difference in height plays a subtle, subconscious role in interactions.

But the story as it was presented (if my memory isn't totally off) didn't bother me. I don't have a built in anti incest thing for others. As long as meaningful consent is present, it's no more my business than it is if you enjoy getting pegged, or like sniffing panties, or anything else that isn't being done with harm.

Now, the teenage with an adult thing is sketchy, but age of consent varies on a legal level, and they never said where they're from. Not that something being legal makes it okay, but it does mean that there's no single consensus on when a person is allowed to exercise their body autonomy via consenting to sex.

However that specific story says the person was 14. That throws a big ol' wrench into the hypothetical gears. That is below the point where I believe consent can be meaningful. Not that it's utterly impossible, but I've never known a single 14 year old that could reach the standard of meaningful. The difference in emotional development just between 14 and 15 is massive. The extra social development is too. So I'm of the mind that, if they story is real, the kid in the story was harmed via their sexual development being thrown off its proper course.

See, that's one of the big issues with teenagers and adults interacting sexually. When age peers interact sexually, there's a degree of similarity in how they approach their acts. It's a mutual learning curve. While there is still some degree of pressure that can occur to push one party past boundaries, that in itself is part of psycho-sexual development.

When an adult is involved, and the teen can't form meaningful consent, all of it becomes out of scale and out of a comfortable pace of progression.

That's where the story turns into one of abuse. There's no way the op of that story could have reached adulthood with a healthy and balanced sexual self. Just not possible. Had it been a one time thing, I could maybe see the story as something to shrug off as "people be trippin". One event isn't inherently harmful. But it didn't even end when the arms healed iirc. So that's proof his normative sexual development was harmed.

To sum up: as an idea, it's less than ideal, but nothing I really care about. As a specific story, the mom did a very bad thing