These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Arc Fatigue: The mystery about who "D" is lasted from Chapters 18 to 24. "D" was falsely hinted at repeatedly with Draco, Kii, and Lilith. Doppel provided the initial note, while Lala wrote the second and final note.
Broken Base: Fans have been split on the official spelling of the characters' names revealed in chapter 10, especially Meer (German for something between "ocean" an "sea")/Miia.
The dislike of the translation choices in the official english manga has caused not so much a split, but a near-unanimous decrying of it. The translation in itself isn't bad or incorrect, it's just filled with a Hurricane of Puns. Which to some people is a lot worse.
Les Yay: Papi and Suu. Suu notably kisses her outright during her water-absorbing spree in Chapter 10, when she settles for lapping up the water from Miia and Centorea.
Chapter 14 sets Rachnera up as the manga's first possible villain, yet she was disappointingly added to the harem near-instantly. It would've been more climatic had she been a slightly longer-term antagonist with a sympathetic backstory that became a love interest.
And then there's Draco from chapter 19. Possible rival and villain...and he turns out to not even be an actual dude.
Not to mention the anticlimax resolution of the "D" mystery. The first letter was a joke. The second letter appeared to have been done by yet another goofy girl. The author got quite the knack to drop what could have been interesting plotlines for slapstick characters.
For the Female we have the fact that them being raped to breed with the strongest males is perfectly acceptable.
For the males we have it to where their culture focused on breeding the strongest to the point they are now GonkDumb Muscle but the females are seen as victims for having to breed with them. Again despite their culture being the reason they are like this and essentially could be seen more as Tragic Monsters.
A funny example. Since Kimihito's death threat, Ms. Smith assigns a member of MON for protective detail during his dates. You'd think Doppel, the shape-shifting infiltrator, would be the perfect candidate for keeping an eye on him incognito; instead, Smith assigns Tio, the dark-skinned, horned giant. There's even a panel where pedestrians look at her in shock while she (futilely) tries to be discreet. Considering Doppel instigated the whole plot, it makes sense she's not available.
In doing this Doppel herself qualifies, as she accomplished the exact opposite of her job. Worse, her prank ended up allowing Lala to send an actual death threat unnoticed, as it was written off initially as another product of Doppel.
Wheelchair Woobie: Averted with Meron. She is chipper, polite, and only needs the wheelchair when she's not in her room, which has a pool of water to accommodate her.
Woolseyism: MON's acronym was changed from "Monsters of a Neuro" to "Monster Ops: Neutralization" in the official English translation, changing a case of Gratuitous English into a name that made sense in English.
In the official English translation, Rachnera's dialogue is riddled with spider puns and uses "itsy bitsy" as an adjective in nearly every single sentence.