My theory that Nathaniel is actually questioning Marinette’s behavior and it upsets him.
Instead of ripping his old comic with Marinette out of his sketchbook or painting it black, Nathaniel decided to draw a cross over it and tape the new fake comic book cover with Ladybug right next to it leaving the old comic visible.
This makes me question how exactly does he feel after his first akumatization. It was his birthday and although he doesn’t remember his date with Marinette, it’s possibly written in news, where Nath could discover Marinette knew about his birthday but after he got purified, there was no scene showing us Marinette actually cared. I mean she’s baker. Couldn’t she just bring some cookies for him, the episode was about him!
In Reverser she even lies to Adrien it’s Nathaniel’s birthday soon and that she’s preparing a surprise for him. However she didn’t bother to do anything when it actually was his birthday.
In Rogercop, Marinette gets accused of stealth by Chloe and rather than face it, she accused everyone else including Nathaniel. She said it could be Nathaniel who stole Chloe’s bracelet because he sketched it. Of course she didn’t blame Adrien, because he’s perfect and he’d never done it. Nathaniel heard it while spill being a suspect standing right in front of her. Although Marinette sais “Lesson learned.” in the end for her self, there’s no scene of her actually apologizing to her classmates she accused including Nathaniel.
Although it sounds surreal that Ladybug would give Marinette her diary so she could pass it to Nathaniel, Nathaniel asks Marinette if it is some kind of prank. After meeting Marc who actually wrote the diary as a fanfiction, Nathaniel automatically jumps into conclusions that it is in fact Marinette pranking him and doesn’t even let Marc to explain. After Alix telling him it’s not like her to make fun of other people, Nathaniel doesn’t admit Alix is right.
And even though he used to be in love with Marinette before and they are still friends, Nathaniel has nothing to say when Marinette gets accused of stealing, harming Lila and gets expelled.
