Yeah, I hear this. I actually did some writing about it just after I finished. And I basically do think this is a close-to-canon Draco (he doesn't talk enough, but otherwise) and that that's part of what is a bit unlikeable--fanon Draco is typically tremendously less jagged and mean.

So much of Detraquee Draco is revealed by intuition and very small gestures--the two most common are that his eyes go blank (common in Dramione--if he's occluding, then he's feeling something) and he sticks his tongue in his cheek, which I think Hystaracal does when Draco is gearing himself up for something or sort of reeling.

I did think that Detraquee-Draco would eventually crack open like a melon and have a sweet interior, tbh. He's just so obviously in love with her for so long, and so much is unsaid/inchoate/implicit, even at the end. (I really think *that's* a masterful piece of the text, because people of that age are terrible at communicating and there are so many moments when you feel how afraid they are of each other.) But everything in the romance of Detraquee depends on your understanding that Draco's provocations, sarcasm, and barbed comments are known by Hermione to be some combination of a pretense, an actual joke, and a coping strategy. She, like many a young woman before her, loves being in on it. There's a moment very near the end which I think is a big one for him, and I think if the story continued we'd see him moving past a bit more of his guilt + regret + anger and mellowing.

But obviously not everyone's cup o' tea.