In the first chapter/episode, Usagi fearfully shows her mom that she has failed her test, only to have her mom verbally berate her and kick her out of the house to "think about what she's done." To Japanese audiences, this is seen as strict, but appropriate punishment for her perceived laziness. To western audiences, looks an awful lot like child abuse. Naturally, the 90s English dub somewhat watered it down to just telling her to go to the library to study.
Usagi says blithely that sleeping forever sounds like fun. Her friends just give her funny looks because their teacher was carried off sleeping on a stretcher, so Usagi seems Innocently Insensitive. In the 2010s, saying you'd like to sleep forever would be a sign of suicide ideation, which Usagi never has during the series even at her lowest points.
Mamoru is a 18-year-old college student and Usagi is a middle school student of 14 at the start of the anime (he's only seventeen and still in high school in the manga). They are a couple after two seasons of heartbreak and misunderstanding (and the American dub did next to nothing to tone it down). Mamoru also dated Rei (same age gap) briefly in the first season and nobody bats an eye. Such serious age gaps between love interests are quite common in anime and manga made around the same time period (see also Glass Mask and Yawara! A Fashionable Judo Girl), and for that matter, are entirely legal and at worst mildly scandalous in Japan, the logic being that an older man will be more capable of protecting and providing for the younger girl. However, in America, Mamoru would be considered an ephebophile or at worst, incorrectly deemed a pedophile and busted on charges of lewd conduct with a minor. In the manga, the two are much closer in age – Mamoru is in high school when he starts out, and doesn't enter college until the final story arc. Usagi entered high school at the start of the Dead Moon Circus arc in the manga, thus keeping their gap not quite so extreme. Still, it is one of the more criticized aspects of their relationship in the West.
The diet episode early in the anime is representative of the extremely thin-obsessed culture of Japan... and all the negative body issues that come along with it. It comes off as even harsher a good twenty years later when body image and eating disorders are gathering far more media attention in the west.note The 90s English dub improves on the script by altering this to the more American-friendly lesson about the dangers of exercising until you drop, urging more healthy methods of getting in shape. Then again, it's also this culture that is being exploited by the villains for their schemes, making it a parody.
Rei's grandfather in the anime frequently sexually harasses teenage girls, and this is treated as a cute character quirk rather than a sign that he's a creep. Even the episode in R where a scandal ensues after the media picks up on his behavior is Played for Laughs. The manga averts this, where he's a Nice Guy who is Older Than He Looks. Unsurprisingly, the DIC dub completely changed his character and rather than flirting, he simply is trying to find people to work at the shrine. Even the more faithful Viz redub tones this down to him just being overly friendly to the girls at the shrine, with no perverted intentions.
In the first Sailor Moon Memorial, which is a non-canon recap of the previous season, part of the narration turns to Zoisite and Kunzite's relationship. When Luna points out that this sort of relationship is far more common today ("today" being in 1992, thus thirty years ago), Usagi starts making gagging noises on the soundtrack. While this comes off extremely poorly in a far more gay friendly world and presents Usagi more harshly, jokes like these were extremely common in the early 90s when gay characters had less media visibility. Notably, in the show itself, which is canon, nobody reacts to their relationship as if it's unnatural at all and in fact the two characters sharing a genuine romance in spite of their horrifically evil deeds is presented as their sole sympathetic traits. Later in the series, Usagi's only concern about Haruka and Michiru's relationship is that she initially took Haruka for a boy and got a crush on her. The show would later portray the gender-swapping Sailor Starlights as pining exclusively over women and none of the cast members reacted as if this was abnormal.note In the manga, none of these types of jokes were present — Takeuchi tended to portray sexuality far more fluidly and was quite adamant about her beliefs that homosexual and heterosexual love were the same. Hence why Usagi figures out Haruka's gender because Haruka kissed her as both her civilian identity and also as Sailor Uranus... and is not upset about being kissed by a woman, but is upset that she might be cheating on Mamoru.
While the relationship between two women was Fair for Its Day (well, not in the 90s dub), some characters weren’t as progressive.
In episode 96, when Makoto seems to be crushing on Haruka, Usagi tells her that she shouldn’t. Not because Haruka has Michiru, not because the Guardians have more important things to do, but because Haruka is a woman. Later, when Haruka and Michiru invite Makoto on a drive, Usagi goes back and tells the others that Mako’s on a date, but the other person is a woman. The other guardians seem to disapprove and Minako, the “Goddess of Love,” asks if Mako changed her orientation. This is changed in the Viz dub, where the Guardians are concerned that Makoto is in love with someone who is already in a committed relationship. Makoto reassures her friends that she has no intention of breaking up Haruka and Michiru. The Cloverway dub also fixed this by having Serena being mad because Lita went out with Amara and Michelle for ice cream without her and being worried that Lita didn't want to be her best friend anymore.
In episode 178, Usagi receives a love letter from a girl, but turns her down because she is already in love with someone, and says that it's "better to fall in love with a boy". Similar to the above example, the line was edited out in the Viz dub.
