Adicionei o seguinte a ~/.emacs
:
(setq-default indent-tabs-mode t)
(setq backward-delete-char-untabify-method nil)
(setq indent-tabs-mode t)
(defun my-insert-tab-char ()
"Insert a tab char. (ASCII 9, \t)"
(interactive)
(insert "\t"))
(global-set-key (kbd "TAB") 'my-insert-tab-char) ; same as Ctrl+i