Fix #38

src/7_finished_example.md

@@ -205,4 +205,13 @@ impl Drop for Reactor {
         self.handle.take().map(|h| h.join().unwrap()).unwrap();
     }
 }
-```
+```
+
+## A little side note
+
+The comments delimiting the Executor, `Future` implementation and Reactor, 
+emphasize on what is part of the langauge (Future and Waker) and what is not (runtime specifics). 
+Therefore, the comments associate the `Waker` with the `Future` implementation,
+despite its strong relation with the Executor.
+
+