Sorry I feel the need to respond to the idea that vase scene is good actually because everyone is flawed in it. I feel like there is something missing in this analysis, and it's that much of the problem with the scene lies less in the scene itself but more in how the scene and the characters' actions within it are followed up by the text.
How the scene plays out in the text is that Winter knocks over the vase while lashing his tail in anger when Moon says Darkstalker is his friend. Winter says that he's evil, Moon responds angrily herself that Winter said he would give Darkstalker a chance, at which point she realizes and Winter confirms that Darkstalker had brainwashed him. Qibli makes the "I'd brainwash you too" comment, says sorry immediately, and then when Winter "turned to Moon as if he was ready for her apology," she turns her back on him and begins picking up pieces of the vase. She, looking to Qibli and Kinkajou but not Winter, insists that Darkstalker only wants what's best for everyone. At which point Winter angrily reveals the Icewing plague. In surprise, she says "What", accidentally steps on a vase shard, and gets a small cut. Qibli rushes to her aid, remarks in the narration that if Winter loved her he shouldn't be yelling at her like this, and then confirms the plague. Anemone comes in with skyfire, winter makes a snide comment about Moon not knowing where she feels about Darkstalker, to which Moon respond sharply that she feels lied to, and then they split up. I'd like to note that when Moon decides to confront Darkstalker, what she initially says to Winter is "Please don't break anything else," before asking Qibli to come with her.
There are three things I'd like to draw attention to:
Moon's injury is small and it's not quite as simple as "Winter injures Moon". She has an accident which compounds on a thing Winter did seemingly on accident.
Moon is not being passively absorbing Winter shouting and making snide comments. She's responding in anger herself, pointedly ignoring him (and how he was personally violated by Darkstalker), and before she leaves to confront Darkstalker, she tells him not to break anything else like he's a petulant child who will wreck the room in anger as soon as he's unsupervised.
Qibli's internal monologue only notes Winter's treatment of Moon as bad
I'll come back to point one, but the other two are not bad, on paper they are good even within a reading of this scene where it is drawing out the flaws in each character present. If these flaws were to be followed up on and the group were to reconcile, and if Moon and Winter were to talk out why each of them were hurt by the argument it would be compelling. The reasons Moon was hurt are obvious, Winter shouts at her and refuses to consider her perspective, that she's been manipulated and didn't know any of this. Winter's aren't so obvious, but still present. Upon being told that Darkstalker had profoundly violated his autonomy, Moon doubles down on Darkstalker just wanting the best for everyone, tacitly implying what Qibli had just been wrong to say outright: that it was on some level justified to do that to Winter. When she learns of the failed genocide, she's expresses being upset about being lied to, but not any of the ways Winter was directly harmed.
And then the books only acknowledge how Moon was hurt by the argument.
In the epilogue, it's made clear that Moon and Winter haven't seen each other in person in some time. Kinkajou tells Winter that he should come visit Moon and apologize to her for being mean, and he agrees and says that he knew after that scene that he had ruined any chance with her. At no point after the argument ends does anyone acknowledge that Winter had legitimate reasons to be upset, that Moon had acted passive-aggressively, that reconciliation would involve all of them acknowledging that they hadn't been at their best in that moment. Only that Winter had been mean, so he should say sorry. Every direct perspective on the argument paints Winter, and only Winter, as wrong in his argument with Moon.
And when you consider the vase with this knowledge, it's just silly. It feels like a thing that is there to make Winter seem meaner, Moon more victimized, and Qibli like a nice supportive guy who would be better for her.
The scene becomes ridiculous when put in the context of the rest of the book, because half of the interesting substance from the character's flaws ends up not mattering. Moon and Kinkajou never have their actions in this scene come up again. Qibli's flaws are instantly addressed so he can resolve them onscreen and complete his arc. Winter spends the rest of the book in the doghouse for it and his actions are used as justification for why he isn't right for Moon. In the context of the book, this scene exists to forward Qibli's arc and justify Moon choosing him, and it does both at Winter's expense.
It doesn't matter if everyone's flaws are on display when the book is picking sides, and deciding who gets to gets to grow from this argument, who doesn't, and who doesn't need to.