PEP 8: try to better explain a somewhat cryptic guideline

pep-0008.txt

@@ -121,9 +121,12 @@ Optional::
       var_one, var_two,
       var_three, var_four)
 
-This PEP explicitly takes no position on how or whether to further
-visually distinguish continuation lines after multi-line ``if``
-statements.  Some acceptable options include::
+This PEP explicitly takes no position on how (or whether) to further
+visually distinguish continuation lines in the header from the nested suite
+in an ``if`` statement, where the combination of a two character keyword, a
+single space and an opening parenthesis creates a natural 4-space indent for
+the expression in the header.  Some acceptable options in this situation
+include::
 
     # No extra indentation.
     if (this