buffers because it modifies them.
When the value is `in-margins', then clickable buttons are
displayed in the margins before the headings.
-When the value is `t', clickable buttons are displayed
-in the buffer before the headings. The values `t' and
+When the value is t, clickable buttons are displayed
+in the buffer before the headings. The values t and
`in-margins' can be used in editing buffers because they
don't modify the buffer."
;; The value `insert' is not intended to be customizable.