Hacker News Reader

.docx is plain text xml though (You can even save explicitly as .xml which has all the images in base64).

Is track changes not good enough?

(1) Now you get to train your office mates who have been emailing .docx files to each other for twenty years in git, specifically to merge XML files.

(2) What happens when someone checks in a hand-reconciled merge that is not a valid XML file, because whoops?