I don't think this is the first time there's been a mistake in the translations with Persona 4. The only one I remember was Naoto referring to Kanji by his last name in the JP version but his first in the US/EU ver. then it appeared as a joke in a arena. I saw someone complaining about what Adachi says after the car crash, the bit that Naoto points out later. Apparently it was more incriminating in the JP game but I've only seen one person mention that.
Hm, those other two you mentioned are true, but not really mistakes. It’s complicated, but I’ll try to explain;
The thing with Naoto refering to Kanji by his last name in the Japanese version is because Japanese Naoto refers to everyone by their last names, when possible. It’s part of her “Detective Novel”-shtick. The Japanese Version made very sure that Naoto sounded like she was taken straight out of a Japanese localized American Film Noir.
Generally, how the characters refer to each other is very different in the Japanese version from how it is in English. They may have “kept” the honorifics, but in many cases they don’t actually match up with the honorifics used in the Japanese version, or the name basis is switched. Japanese Yosuke calls Chie and Yukiko “Satonaka” and “Amagi-san” respectively. Japanese Junpei calls Yukari “Yukaricchi”, rather than “Yuka-tan”. In fact, in the Japanese version of P4U(2), nobody ever refers to “Yu” as “Yu”, but almost everyone refers to him as “Narukami” (Interestingly including Yosuke, despite the fact that he occasionally switches to first-name basis with Yu in the (japanese) Anime and during his (Japanese) Social Link in the game, if I remember right.) Same is true for Ken; *nobody* (except Teddie) ever refers to him as “Ken” in the Japanese version; it’s always “Amada”. What I find especially interesting is that, while in the English version nobody ever uses honorifics for Teddie, in the Japanese version, everyone uses *different* honorifics for him, some of which aren’t even really honorifics. Yosuke calls him “Kuma” or “Kuma-kichi”, Kanji calls him “Kuma” or “Kuma-kou”, Chie alternates between calling him “Kuma-kun”, “Kuma-kichi” and “Kuma-kou”. Yukiko and Nanako call him “Kuma-san”, Rise and Naoto call him “Kuma-kun”. "-kou" and "-kichi" aren’t actual honorifics, "Kuma-kou" is a pun on "Kumakou-Hachikou" which means "Average Joe" and "Kuma-kichi" is a play on the unisex name "Kumakichi", which means "Lucky Bear". (Yeah, that’s right, in the Japanese version, people use puns to refer TO Teddie. How the tables turn…)
Somebody actually once did a table of how P3 characters refer to each other in the Japanese version. It’s really amazing how different it is. These changes were made to simplify the rather complex ideas of “Name bases” that the Japanese have for the western audience, since in Japan, whether first or last names are used among friends and whether or not a honorific is used (and which) says a lot about these people’s relationship when put into the right context (!!!). For example, I once almost happily jumped through a roof because a friend in Japan asked me to call her [First Name]-chan. It’s that big of a deal to be allowed that, because depending on context, the honoriffic “-chan“‘s meaning can range from loving or endearing to demeaning and disrespectful. Since most of the western audience lacks the necessary context, the localization team choose to simplify it. So while there is a good reason for that translation choice, we still lost a lot of nuances due to it.
As for the Adachi bit, that’s sorta true, it’s that the verb Adachi used in the Japanese version was much more unmisunderstandably “to toss someone into something”, which could not have been misunderstood as a figure of speech, unlike in the English version. The problem here is the English verb just being a little more ambiguous, so it would have been hard to evade this problem.
Can you see why I consider translation an art?