The Most Dangerous Minor Mode, as the name says, is a particularly dangerous Emacs minor mode. It’s inspired by the website “the most dangerous writing app”.
If you don’t type at least one key every
tmd-timeout, (by default 5 seconds) the whole buffer will be deleted (the narrowing will be respected).
You can enable and toggle it with
M-x tmd-minor-mode RET.
It doesn’t delete the undo history, this is probably a bug ;)