Hit C-x =, mark a region, C-M-c to confirm, mark a second region, C-M-c to confirm and you have an ediff of regions of the same buffer

ediff-regions-samebuffer.el

  (defun ediff--regions-samebuffer (ediff-regions &optional startup-hooks)
    (let ((cloned-buffer (clone-indirect-buffer-other-window nil t)))
      (unwind-protect
          (funcall ediff-regions (current-buffer) cloned-buffer startup-hooks)
        (kill-buffer cloned-buffer))))

  (defun ediff-regions-samebuffer (&optional wordwise startup-hooks)
    "Ediff two regions of the same buffer, automating the clone-and-narrow dance.
Optional interactive argument WORDWISE to do a word-diff instead of line-by-line."
    (interactive "P")
    (if wordwise
        (ediff--regions-samebuffer #'ediff-regions-wordwise startup-hooks)
      (ediff--regions-samebuffer #'ediff-regions-linewise startup-hooks)))

  (global-set-key (kbd "C-x =") #'ediff-regions-samebuffer)