A major theme is the concept of vulnerability. Luna may seem strong in her own way, but she also has her vulnerable moments. Harry's protection is a response to that. In many fanfictions, this also ties in with the theme of loyalty. Harry is loyal to Luna, and his protection is a manifestation of that loyalty. It shows that he will be there for her no matter what, whether it's facing dark forces or just the everyday nastiness at Hogwarts.
One great 'Harry is protective of Luna' fanfiction is 'The Protector's Promise'. In this story, Harry's protective nature towards Luna is shown through various dangerous situations they encounter at Hogwarts. Another one could be 'Luna's Guardian', where Harry stands up for Luna against bullies.
In some versions, Neville could also be one of Harry's protective mates. Neville, who grows in courage throughout the series, would be willing to stand up against any threat to Harry. And Luna, with her unique perspective and magical abilities, might also be part of Harry's protective group.
Maybe Blaise sees something special in Harry. In fanfiction, it could be that Blaise admires Harry's courage or his unique abilities. He might feel a sense of kinship with Harry despite their differences.
Well, it could be that in the fanfiction's plot, Harry has some special qualities or is in a dangerous situation. Edward, being a character with his own set of values, decides to be protective. For example, if Harry has some sort of power that others might want to misuse, Edward would step in to safeguard him. It might also be related to their shared experiences or a bond that has developed between them over the course of the story.
Well, in some fanfictions, Snape might be protective of Harry because he sees a lot of Lily in Harry. Lily was Snape's long - loved friend, and Harry is her son. So that connection makes Snape feel an urge to protect Harry from harm, despite their often - rocky relationship in the original story.
One reason could be the complex relationship they have in the original series. Fanfic authors often expand on that. Maybe Draco realizes Harry's importance in the fight against the real evil, like Voldemort, and so he becomes protective. It also adds an interesting dynamic to the story, making it more appealing to readers who love exploring different character relationships.
In fanfiction, Harry might be protective of Teddy because Teddy is Remus and Tonks' son. Harry has a strong sense of loyalty and he may feel a great responsibility towards Teddy as he lost his parents. Also, Harry has his own experience of growing up without parents, so he doesn't want Teddy to go through any hardships alone.