I sympathise! I've even prepared a little note for reviewers suggesting how to get less unreadable results; essentially, think before you type – now there's a radical concept! – and mark up larger blocks (where possible) rather than a word here and there in the same phrase. When I'm editing, I often send back an interim version with original/edited side by side in a table …

@Charles – away from Word, I use conditional text and turn off display of deleted blocks/remove highlighting from new blocks once the changes are no longer important; in Word, I guess I could adjust the Deleted character style to 'hidden text' for similar behaviour. (I have about twenty releases of a regulatory document in a single source-file, and could go back to and adjust show/hide conditions to reproduce any release; easier, of course, to check the row of binders and pull out the appropriate hard copy, but traceability was a requirement)