Why and How I Wrote My Academic Book in Plain Text
Another huge reason to use plain text that he didn't mention is version control. With plain text, you can check the files into a git repo and diff any two commits. You then get all the advantages of working with version-controlled code, e.g. commenting on diffs.Word and Google Docs do save revision history, but they slow to a crawl when you have a document with a lot of pages, to the point of being unworkable.