My syntax is not identical to the syntax proposed there, and in was chosen, in part, to avoid some of the issues that were responsible for its rejection. 

The reasons given for rejection were "open issues" and "some confusion between ranges and slice syntax". 

For the latter, part of my reason for using parentheses instead of brackets is to avoid potential confusion.  So without knowing what specific confusion was being referred to I can't say whether this complaint is relevant or not.

For the open issues, all of the issues are either no longer relevant in python 3 or are not applicable to my proposed syntax.  The first is fixed by the python 3 range type, the fourth is fixed by the elimination of the long type in python 3, and the second, third, and fifth are not relevant to my proposed syntax (in fact I chose parentheses instead of brackets partly to avoid ambiguities and complications like these).