(defvar outline-minor-mode-prefix "\C-c") outcommented, since it does not

really take effect here (must be set in init-file before outline is loaded)
and "\C-c" conflicts with other important modes, e.g ESS.

outshine.el

@@ -132,12 +132,13 @@ Used to override any major-mode specific file-local settings")
 
 ;; ** Vars
 
-(defvar outline-minor-mode-prefix "\C-c"
-  "New outline-minor-mode prefix.
-Does not really take effect when set in the `outshine' library.
-Instead, it must be set in your init file *before* the `outline'
-library is loaded, see the installation tips in the comment
-section of `outshine'.")
+;; ;; "\C-c" conflicts with other modes like e.g. ESS
+;; (defvar outline-minor-mode-prefix "\C-c"
+;;   "New outline-minor-mode prefix.
+;; Does not really take effect when set in the `outshine' library.
+;; Instead, it must be set in your init file *before* the `outline'
+;; library is loaded, see the installation tips in the comment
+;; section of `outshine'.")
 
 ;; from `outline-magic'
 (defvar outline-promotion-headings nil