The old technique for disabling autosave and re-enabling traditional text editor behavior (i.e., NOTHING get saved unless one saves it EXPLICITLY) of
defaults write com.apple.TextEdit ApplePersistence -bool no
that worked at least up to and including El Capitan, no longer works in Mojave!
Does anybody know of a way that does work? Or know of a text editor that works the way TextEdit used to work?
Note: Since my original post, I've tried Bean (it seems to do a lot of formats other than plain text), a Mac port of GEdit (as clunky as I remember it), and TextWrangler (it works, but doesn't appear to do anything but plain text; RTF capability would be a plus).
An early (since deleted without a trace) reply indicated that rather than an auto-save, the current TextEdit acts directly on the file contents. This is rather disturbing, if true, but it would certainly explain why, with the "Ask to keep changes when closing documents" flag set in System Preferences/General, the "delete/cancel/save dialog" on a saved file becomes "revert/cancel/save."