This is completely inappropriate. Fanfiction should be about exploring characters in a way that is in line with basic human values. This kind of description goes against decency and respect, and it is not something that should be part of any fan - based creative writing.
One negative impact is that it spreads immoral and vulgar ideas. It can also make the original work's fan community look bad as it goes against the positive and creative nature that fanfiction should have.
One way could be to make it a comical misunderstanding. For example, Harry is forced by a magical prank gone wrong to 'suck' on a lemon drop that Snape always has, and it's all just a big, silly situation that makes for a humorous moment between their otherwise tense relationship.
It could be a plot device used by the author of the fanfiction. The touch might be used to create tension or an emotional moment between Snape and Harry. It could signify a turning point in their relationship, whether it's the start of a more positive understanding or the heightening of an existing conflict. For example, the touch could make Harry feel uncomfortable and lead to a confrontation later, or it could make him realize that Snape has a more complex side than he initially thought.
Draco could be made to stand in the corner of the classroom during the entire potions class as a punishment. This would be a public humiliation for him, especially in front of his peers. It would also show Snape's no - nonsense attitude towards misbehavior.
This could potentially be a very dark and forced power - dynamic exploration in a non - sexual way. Maybe it's about Harry being forced by some dark magic or a plot device to perform an act that goes against his will towards Snape, symbolizing the complex and often adversarial relationship between them in the original series.
It could initially create more tension. Harry might be suspicious of Snape's motives, especially considering their generally strained relationship. He could start to wonder if Snape is up to something malicious.
It is completely unethical. Forcing any form of inappropriate or sexual behavior, even in the context of a story, violates basic principles of respect, consent, and human dignity. No one should be made to engage in any such demeaning act in any situation, real or fictional.
In a 'Hermione forced by Snape' fanfiction, it might involve Snape forcing Hermione to study a particular type of magic that she is not interested in. For example, dark arts related magic for some convoluted reason. Hermione, being the intelligent and headstrong witch she is, would likely resist at first but then find a way to turn the situation to her advantage. She could use her knowledge to outwit Snape and perhaps expose his true motives to the other Hogwarts faculty.