Her "reason and maturity," in canon, is basically playing the role of a responsible young girl. Rowling seems to think this is impressive; obviously, Eliezer does not.

I kind of recently came to the realization that I think Eliezer meant Harry and Hermione's relationship to personify what he says often, which is "Utilitarianism is what is correct, virtue ethics is what works for human beings".

It's been a while since I've read canon, but I remember that Hermione as largely motivated by love of learning (with loyalty to her friends as a strong second, but we don't see the two motivations in conflict, and loyalty isn't distinctive to her-- all the good characters are loyal), and HermioneMOR as largely motivated by wanting to maintain her self-image. MORHermione isn't as awful as that might be because the self-image she wants to match is (mostly?) built around virtue ethics, not vanity or status, but the two characters are very different to me.

From my point of view (and I don't know if anyone shares it), in the early parts of MOR, Hermione was this weird brittle conglomeration of traits that didn't even seem like a human being. I blew up about it, and upset Eliezer, and he did something to how Hermione was portrayed, I don't know what, so that she didn't make me crazy even though her character wasn't drastically changed. I leave the possibility open that Eliezer being affected by what I said calmed me down rather than that he changed the character, though I certainly didn't intend to affect him that strongly.

I have to take it on faith that Eliezer and practically everyone here likes MORHermione as much as they say they do because this isn't how I react to the character.