It gives fans a chance to explore different 'what - if' scenarios. By seeing the Avengers' reactions, fans can get a deeper understanding of the characters.
Some fans might be disappointed. Fanfiction often allows them to explore different scenarios with Naruto's character. If he gives it up, it's like closing a door on those creative possibilities.
The Naruto fandom would likely be very divided. Some fans would be extremely outraged as it goes against the core values and character of Naruto. They might condemn such a fanfiction.
On the other hand, there would be fans who would welcome it. Maybe they never liked the pairing in the first place or they think it adds an interesting twist to the story. They could start exploring new relationships for both Sasuke and Sakura in their own fan - created stories.
The Naruto fandom would probably react very negatively. Fans are used to seeing Naruto as a hero, a symbol of hope and growth. A fanfic that portrays him as a slave goes against the very essence of what Naruto represents. There would be a lot of criticism on social media platforms, and many fans might even call for the fanfic to be removed or boycotted.
In the absence of knowledge about the 'Big Mouth Vader Johan' story, Big Mouth could be a descriptive name for a character who is overly chatty or has a unique oral feature. Vader might be related to the idea of a strong, authoritative figure, similar to the Star Wars character Darth Vader. Johan might be a common name for the protagonist in this story. It's possible that these three elements - the talkative Big Mouth, the powerful Vader - like figure, and Johan - interact in various ways within the plot of the story, but without the story itself, it's hard to be certain.
The fandom's reaction would be quite mixed. Some fans, who are more open to extreme and creative interpretations in fanfiction, might find it an interesting and bold take. However, the majority would probably be horrified. Snape is a beloved and complex character, and this idea of him being aroused by Harry fanfiction is so far from what J.K. Rowling created. It could lead to a big debate within the fandom about the limits of fan - created content and how it should respect the original source material.