If Harry is a central character, his not stirring could be a turning point. It might cause other characters to react in different ways. Some might be concerned, while others might see it as an opportunity. This then drives the plot forward as different characters' actions and reactions are intertwined.
It could mean that in the context of the fanfiction, Harry was in a situation where he was expected to stir, perhaps react or move in some way, but he didn't. Maybe he was in a state of shock or deep thought that made him remain still.
Yes, in some fanfictions, Harry can be overpowered. It often makes the story less suspenseful. For example, if he can easily defeat every enemy without much effort, the tension and excitement of battles are lost. Also, it might change the relationships with other characters. Since he doesn't need much help, his friends become more like sidekicks rather than equal partners in the adventure.
It can make the readers more aware of the vulnerability of Harry. In the original story, he overcomes many challenges, but in these fanfictions, the added abuse aspect shows how much more difficult his life could have been.
Well, Harry getting younger might change the power balance between him and Draco. It could also lead to more protective or nurturing moments. And it might even impact how they view each other and their past conflicts.
It could strain their relationship. The slap might create a rift between them, making them both question their feelings for each other. Harry might feel hurt and confused, while Ginny could regret her actions but also be stubborn about not apologizing right away.
It can change the story by adding an element of mystery. Since his appearance is altered, other characters' reactions change. For instance, if he looks like a villain, some might be scared or try to fight him.
Deadly pets in Harry Potter fanfiction can add a great deal of danger and excitement. For example, if a character has a basilisk as a pet (even if it's an illegal and dangerous choice), it can create a lot of tension. Others might be in constant fear of being petrified by its stare.
It can create a turning point. For instance, if the main character's wand explodes, they are suddenly left without their most important magical tool. This forces them to find alternative ways to use magic or rely on their friends more, adding a new dimension to the story.
It can lead to a shift in focus. Instead of Harry being the main driving force, other characters get a chance to shine. For example, Hermione or Ron might become more central to the plot.
The blocks could change the direction of the story. For instance, if a block prevents Harry from using a certain magic spell he planned to use, he may have to find an alternative way, leading to a different plotline. They can also create character development. As Harry tries to deal with the blocks, he may grow in his magical abilities or in his understanding of the magic world in the fanfiction.