Ask HN: I'm trying to find a demo video of a text editor on a tablet

I saw a demo video not that long ago (within six months?), probably on HN. Someone (the developer?) was demoing, on a tablet I am pretty sure, an interface for document editing where you could highlight quotes, drag them around, insert annotations, and do a bunch of sorting of these things.<p>I remember it being interesting and can't find it anywhere.