add Guido's comment about nested decorator problems

pep-0318.txt

@@ -229,6 +229,24 @@ suggests nesting of namespaces that doesn't exist.  The name ``foo``
 would actually exist at the same scope as the using: block.  Finally,
 it would require the introduction of a new keyword.
 
+The obvious alternative that nests the function within the block
+
+::
+
+    using:
+        dec1
+        dec2
+        ...
+        def foo(arg1, arg2, ...):
+            pass
+
+has its own set of drawbacks.  Having the minimal indent level be
+three deep for methods is painful for those using limited-width
+windows.  The inconsistent indentation between methods of the same
+class with and without decorators would be a readability problem.
+Finally, adding or removing decorators would require reindenting the
+entire function/method body.
+
 Guido proposed and implementated a patch to support interpretation of
 a `list of decorators`_ as a prefix to function definitions ::
 
@@ -285,7 +303,9 @@ There is some history in Java using @ initially as a marker in
 `Javadoc comments`_ and later in ... mumble mumble ...  The fact that
 @ was previously unused as a token in Python also means it's clear
 there is no possibility of such code being parsed by an earlier
-version of Python, leading to possibly subtle semantic bugs.
+version of Python, leading to possibly subtle semantic bugs.  That
+said, @ is still a fairly arbitrary choice.  Some have suggested using
+| instead.
 
 For syntax options which use a list-like syntax (no matter where it
 appears) to specify the decorators a few alternatives were proposed: