The Dursleys would likely be very unwelcoming. They don't like anything to do with magic or Harry's wizarding world friends.
The Dursleys would probably be horrified. They have always tried to keep Harry's magic life away from their normal, non - magical existence. When Luna shows up, with her dreamy and magical air, they would see her as a threat to their 'normal' life. They might try to be rude and dismissive towards her, but Luna might not even notice their rudeness as she is in her own little world half of the time.
Maybe Luna's unique personality would shock the Dursleys. She might say some strange but profound things that leave the Dursleys completely bewildered.
The wizarding world would likely be in shock. Harry was seen as a hero, and this act would completely change their perception of him. Some might think he was finally getting revenge for all the abuse he endured, but many would condemn his actions as murder is still a serious crime in the wizarding world.
They would likely be disgusted. The Dursleys are so anti - magic that any form of fan - created stories about the magical world would be abhorrent to them.
The Dursleys' reaction would be complex. Vernon would be enraged and might even try to burn any fanfiction he found. Petunia would be conflicted. Part of her would be disgusted, but a small part might be a bit curious as she has some connection to the wizarding world through Lily. Dudley might be more interested than his parents, especially if the fanfiction had some action or adventure that appealed to his more adventurous side.
The Dursleys would most likely be horrified. They have a deep - seated hatred and fear of magic, and Ron and Hermione are clear representatives of the magical world. Vernon might turn red in the face and start shouting, while Petunia would clutch her pearls and Dudley would cower behind them.
Some characters might be confused. For instance, Hagrid would probably scratch his head and wonder what this strange little card is. The strict teachers like Snape might be suspicious and think Harry is up to no good.
Hermione would approach the situation with her typical rationality. She'd remind Harry of the importance of using magic responsibly, even when getting revenge. However, she'd also be secretly pleased that Harry is standing up to his abusers. Ron would be extremely excited and would offer to help Harry in any way he can. He might even bring some of his family's old prank - related magic items to assist. As for Luna, she would see it as an interesting experiment in karma. She'd probably offer some very unique and out - of - the - box ideas on how Harry could get back at the Dursleys in a way that's both satisfying and magical.
They would be devastated. Harry has many friends and allies. People like Hermione and Ron would be heartbroken and would probably seek revenge. The Hogwarts faculty would also be deeply affected. Dumbledore, if he's still alive in the fanfiction, would feel a great sense of guilt for not protecting Harry better. There might be a split in the wizarding community, some believing the Dursleys were acting on their own, others suspecting a darker conspiracy.
They'd probably be horrified. The Dursleys are very much against the idea of magic, and fanfiction might introduce even wilder ideas about the wizarding world.
Hermione would be heartbroken. She would probably try to find out the exact cause of Harry's death, suspecting the Dursleys' negligence or worse. Ron would be furious with the Dursleys and would want justice. Dumbledore would be deeply saddened as he had placed so much hope in Harry. The Weasley family would also be in mourning, having considered Harry as one of their own. And Voldemort would be triumphant, thinking that his greatest obstacle was removed.