org.texi: Fix documentation about C-RET and M-RET

* doc/org.texi (Structure editing): Fix documentation, which is no
  longer in sync with the current behavior of the commands.

doc/org.texi

@@ -1425,26 +1425,21 @@ See also the option @code{org-goto-interface}.
 @vindex org-M-RET-may-split-line
 Insert a new heading/item with the same level as the one at point.
 
-If the cursor is in a plain list item, a new item is created (@pxref{Plain
-lists}).  To prevent this behavior in lists, call the command with one prefix
-argument.  When this command is used in the middle of a line, the line is
-split and the rest of the line becomes the new item or headline.  If you do
-not want the line to be split, customize @code{org-M-RET-may-split-line}.
-
-If the command is used at the @emph{beginning} of a line, and if there is a
-heading or an item at point, the new heading/item is created @emph{before}
-the current line.  If the command is used at the @emph{end} of a folded
-subtree (i.e., behind the ellipses at the end of a headline), then a headline
-will be inserted after the end of the subtree.
-
-Calling this command with @kbd{C-u C-u} will unconditionally respect the
-headline's content and create a new item at the end of the parent subtree.
-
-If point is at the beginning of a normal line, turn this line into a heading.
+If the command is used at the @emph{beginning} of a line, and if there is
+a heading or a plain list item (@pxref{Plain lists}) at point, the new
+heading/item is created @emph{before} the current line.  When used at the
+beginning of a regular line of text, turn that line into a heading.
+
+When this command is used in the middle of a line, the line is split and the
+rest of the line becomes the new item or headline.  If you do not want the
+line to be split, customize @code{org-M-RET-may-split-line}.
+
+Calling the command with a @kbd{C-u} prefix unconditionally inserts a new
+heading at the end of the current subtree, thus preserving its contents.
+With a double @kbd{C-u C-u} prefix, the new heading is created at the end of
+the parent subtree instead.
 @orgcmd{C-@key{RET},org-insert-heading-respect-content}
-Just like @kbd{M-@key{RET}}, except when adding a new heading below the
-current heading, the new heading is placed after the body instead of before
-it.  This command works from anywhere in the entry.
+Insert a new heading at the end of the current subtree.
 @orgcmd{M-S-@key{RET},org-insert-todo-heading}
 @vindex org-treat-insert-todo-heading-as-state-change
 Insert new TODO entry with same level as current heading.  See also the