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.
Base Breaker: Kou. Lots of fans dislike him for choosing to be with Yui, well aware she is guilt-tripping him to keep her company, instead of pursuing Futaba.
Surprisingly, after chapter 34, almost anyone can be a Base Breaker to the fandom depending on who you ask. The current contenders are:
Futaba. Half of the fandom insists that she's considerably a horrible role model because of her choice to start dating Touma, claiming that she's forcing herself to fall in love with him. However, others applaud her as a strong female lead for moving out of a toxic relationship and making decisions on what makes herself happy instead of being a cliched Love Martyr.
Touma. Some fans claim that he's been pressuring Futaba to move on from Kou and date him, while others say that he's a better match for Futaba because he gives her the care and consideration that Kou doesn't.
Shuuko, for some reason, is also being hated for being the ultimate cockblock for Kou. Some say that she's only looking out for Futaba's well-being, but her detractors claim that she has no right to decide what's best for Futaba (even though they never said anything about Futaba when she did the same thing to Yui about Kou). People even take a step further to blame Shuuko's (failed) relationship with Tanaka-sensei and project it as a cause for her actions even though it literally had nothing to do with it.
Die for Our Ship: Yui and Touma get the brunt of the hate from Kou/Futaba shippers.
Kou's also the subject of a lot of anger from Touma/Futaba shippers.
Hilarious in Hindsight: A user on tumblr made a hypothetical fan cast should the series ever get a live-action production, one of them including Yudai Chiba being suggested for the role of Touma. Now that a live-action production is being made, and the casting for the main characters have been released, much of the fandom was excited.
Misaimed Fandom: The main point of the story is youth — growing up — AKA teenagers making mistakes and learning from them. Io Sakisaka intended for readers to watch the characters grow up in their own ways. Unfortunately, with the release of every chapter, you still have people complaining why Futaba still isn't dating Kou,
Ron the Death Eater: Fans, especially the more hardcore Die for Our Ship fans, tend to exaggerate Touma's flaws, especially when it comes down to Futaba, even though in his position it would be natural he would be more careful about keeping his girlfriend close to him.