Clarifying (I hope) text and example added

addressing #980 and #9777

CppCoreGuidelines.md

@@ -20294,10 +20294,6 @@ When declaring a class use the following order
 
 Use the `public` before `protected` before `private` order.
 
-Private types and functions can be placed with private data.
-
-Avoid multiple blocks of declarations of one access (e.g., `public`) dispersed among blocks of declarations with different access (e.g. `private`).
-
 ##### Example
 
     class X {
@@ -20309,9 +20305,33 @@ Avoid multiple blocks of declarations of one access (e.g., `public`) dispersed a
         // implementation details
     };
 
-##### Note
+##### Example
 
-The use of macros to declare groups of members often violates any ordering rules.
+Sometimes, the default order of members conflicts with a desire to separate the public interface from implementation details.
+In such cases, private types and functions can be placed with private data.
+
+    class X {
+    public:
+        // interface
+    protected:
+        // unchecked function for use by derived class implementations
+    private:
+        // implementation details (types, functions, and data)
+    };
+
+##### Example, bad
+
+Avoid multiple blocks of declarations of one access (e.g., `public`) dispersed among blocks of declarations with different access (e.g. `private`).
+
+    class X {   // bad
+    public:
+        void f();
+    public:
+        int g();
+        // ...
+    };
+
+The use of macros to declare groups of members often leads to violation of any ordering rules.
 However, macros obscures what is being expressed anyway.
 
 ##### Enforcement