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.
Was Nanoha justified in harshly calling the Queen out on how she raised Serenity? Additionally, was this in character for Nanoha, who is more responsible than Usagi or Serenity, or was this contrary to someone who would "befriend" her enemies? Or was Nanoha pushed too far with memories of her past life returning and called her out due to a Despair Event Horizon?
Vivio defeating Chibi-Usa and causing her and her alternate timeline to disappear was also a controversial action, especially since it was essentially killing her. Word of God has clarified, however, that Picoha was the aggressor, attacking without stating her intent, and Vivio tried to defeat her non-lethally, without knowing what would happen to her.
Critical Research Failure: In the final chapter, one of the youma, who happens to be capable of Voluntary Shapeshifting, uses Reinforce's form to get close to Hayate and Signum. Unfortunately for her, she exposes herself by addressing them as "you two" while Signum was in a unison with Rein Zwei. Rein Zwei called her out on it, and Signum took her out.
Moral Event Horizon: Precia crosses this in even Fate's eyes when she attacks Alicia for refusing to stand aside and let her continue to torture Fate.