motivate the use of [...] instead of various alternatives.

pep-0318.txt

@@ -206,6 +206,20 @@ effects of the list, is already legal and thus creates a special case.
    http://python.org/sf/926860
 
 
+Why [...]?
+----------
+
+For syntax options which use a list-like syntax to specify the
+decorators a few alternatives have been proposed: '[|...|]',
+'*[...]*', and '<...>'.  None have gained traction.  The alternatives
+which involve square brackets only serve to make it obvious that the
+decorator construct is not a list.  They do nothing to make parsing
+any easier.  The '<...>' alternative presents parsing problems because
+'<' and '>' already parse as un-paired.  They present a further
+parsing ambiguity because a right angle bracket might be a greater
+than symbol instead of a closer for the decorators.
+
+
 Current Implementation
 ======================