The original series has a certain code of conduct and relationships between characters. In this fanfiction, by having Harry tell Molly to shut up, it breaks the harmony and respect that was there. It might introduce a new and darker aspect to Harry's character that wasn't present in the original where he was more polite and deferential to Molly, especially considering she was like a mother figure to him.
It can make Harry seem more hot - tempered. Instead of always being the patient hero, beating up Malfoy shows his impulsive side. He's not just the boy who waits for the right moment to fight Voldemort, but someone who can take immediate action when his friends or his own pride is at stake.
Maybe in the fanfiction, Molly was being overbearing. Harry might have been frustrated with her constant interference or mothering in a particular situation.
A common plot is that Malfoy spreads false rumors about Harry in the wizarding world. This causes problems for Harry, like making some students avoid him or look at him with suspicion. When Harry finds out that Malfoy is the source of these rumors, he gets angry and beats him up. There are also fanfictions where Malfoy tries to get Harry expelled from Hogwarts by framing him for something he didn't do. Harry, being the brave character he is, doesn't take this lying down and gives Malfoy a good thrashing.
It could be a turning point in the plot. For example, if he throws up after being poisoned, it might lead to a search for the culprit and a whole mystery - solving arc. His friends or family might get involved in finding out who did it and why.
Yes, there are quite a few out there. Some explore alternate universes where Harry has different loyalties or family connections. You can find them on popular fanfiction websites by using relevant search tags.
Malfoy is often arrogant. He comes from a pure - blood wizarding family and he likes to show off his family's status. He frequently bullies Harry and his friends.
Yes, there are some interesting 'Harry Potter is Malfoy' fanfictions out there. Some explore an alternate universe where they have a different relationship, perhaps more of a friendship or an alliance against a common foe. These fanfictions can offer unique perspectives on the characters and the wizarding world.
It might also indicate a newfound curiosity. Fanfiction often takes characters in different directions. Harry could be squinting at Malfoy because he's starting to see a different side of him. Maybe he's noticed something that makes him think Malfoy isn't all bad, and the squint is his way of trying to understand this new Malfoy better.
Yes, it can be quite popular. Some fans enjoy exploring alternative storylines and relationships. Fanfiction often takes existing characters and creates new scenarios. In this case, the idea of Harry Potter being related to an Orion Malfoy fanfiction might intrigue those who like to see different interpretations of the Potterverse.