[laserbeam]

That is exactly what I meant. The simplest UX you can have for arbitrary notes of any kind, scribbles, drawings, highlights, is to not encourage page reflow. You can come up with a bunch of other funky weird technical solutions, but once the user hits them there's a strong chance of confusion.

For tablets which encourage writing on your document, the rm2 approach of "just render epub as you would a pdf" feels by far like the best strategy.

The original epub is still stored within their document format btw. You could technically still do things with that file if you wanted.