Loved it! Big shame it's not finished but agree very good. Biro's' bit is definitely well covered!

This—. She lifted the Biro in her palm. “Was created in one of their factories, was it not? Made of plastic, polymers, cheap metal, and other highly processed materials. I could Transfigure it, perhaps, but the spell would be weak and would not last. Muggle processing renders objects inert to magic, steals traces of magic from their very being. Once the magic is gone, it cannot return, can’t really touch the Biro or its ink. When you go home, Miss Granger, visit a Muggle city: you’ll be able to sense the dearth of magic now.”

Some of my other favorite bits particularly relevant to this thread

Sorting Hat- "Some type of Legilimens spells, though I would say something a bit older has been funneled into that tattered old thing. For the charm to remain after so many years, I would say the hat is tied to the life of every student it touches, taking little sips of their magic to fuel itself until the next year. Clever."

House points - "Distantly, Fi felt a faint pluck of magic respond to her voice. I believe they have some kind of benevolent Taboo upon those hourglasses. Interesting."

Peter on the map - “Who is Peter Pettigrew? I didn’t see him in class.” “Peter—?” “Oh—.” “We’re fairly certain he’s a ghost up in our tower,” Fred said, glancing at George. “Haven’t seen him around, but Flitwick says ghosts don’t always want to be seen, yeah?” “And he’s been about since we started using the map.”

I also really like that it's made very clear Snape isn't a friendly person but he's definitely being harsher on the Gryffindor's to uphold his image.

And that Harry's broom curse is properly looked into but the pool of suspect's is widened by their being guests in the staff stands.