FWIW[+], two-and-a-half suggestions for playback mode:

- mark the current edit point more prominently,

- automatically scroll to where the edits are taking place (obvious if you test this on a small screen),

- if you implement the former suggestion, signal big jumps prominently in a way that helps viewers keep track of where they are in the overall document.

[+] I know this is an early proof-of-concept for playback mode, and my suggestions are probably obvious, but it can't hurt.