Although in third person, Harry Potter is definitely narrated from Harry's point of view with the exception of the occasional chapter that takes place elsewhere. And as such, I've picked up on some of his speech patterns. For example, he almost always calls someone of his age group by their first name ("Dean" instead of "Thomas"), even if they're on bad terms ("Ernie" instead of "Macmillain.") Older students he varies; he tends to use last names unless if he's friendly with them ("Diggory" became "Cedric" after the Triwizard Tournament) with the exception of Oliver Wood. Slytherins are always by the last name ("Malfoy," "Crabbe," "Goyle") however he consistently uses first names with females whether he knows them well or not and even if they're in Slytherin ("Pansy" instead of "Parkinson," "Millicent" instead of "Bulstrode"). If he meets a student's parent, he will call them by title to differentiate them from the child ("Mr. Malfoy" for Lucius) and he very, very rarely calls an adult by their first name even if they're close. And now I'm stepping into controversy: If he meets a black person, he will instantly note their race, which is why I don't think Hermione Granger is black, but he doesn't for other races.

These small nuances is what makes a character unique and creates layers to their personalities. It shows how they view other people and how they regard their relationships with them. Harry is respectful toward his elders, but with his godfather, the one person he views as a surrogate father, he calls him "Sirius." And if you're going to translate this type of stuff, you need to pay attention to these to retain the richness. For example, let's look at this:

This completely threw me off because the speaker always calls him by his last name, Okumura-kun. I've always taken note of this because I found it weird to call him that when they're brothers. So I checked the original and the line is, "君もこちらへ." Yeah, he didn't call him Rin! The translator just fucked up!

These kinds of discrepancies are all over the place in many different series. If you make these types of errors, then fans start treating these words as gospel and write long-ass essays about stuff that isn't even right. I would not be surprised if I found a post saying these two brothers' relationships has strengthened now that they're on a first-name basis, even though it's completely, utterly wrong. Admittedly for scanlations the groups aren't being paid for this, but I would hope if you like a series so much that you dedicate your spare time to translate it, you would notice these nuances.

What concerns me particularly about the picture above is I believe it's from the official translation. Meaning someone was paid for that fuck up.