To relate this back to the blog post, the original sin is that Python has too much syntax. Every time somebody wants to add a "language" feature, it has to be implemented with some kind of syntactic change, and support for the semantics of the feature has to be added to the interpreter. That's a lot of work, and it means that alternate implementations like Jython can't keep up.
A good example of this is generators. Via PEP 255 they were introduced in Python 2.2, and required the addition of the "yield" statement to the syntax. Recently Squeak (an open-source Smalltalk implementation) added generators to the standard library, with no syntax changes required. It was a much smaller project, and the change can easily be ported to other Smalltalk implementations without participation from the maintainers of the core libraries or virtual machine.
So languages with very simple syntax, like Smalltalk and Lisp just don't suffer from the high level of language evolution friction that Python does. In practice, the diversity of dialects and the ease with which the language can change creates the kind of market system of language features that andreyf mentioned here on HN.
The neat thing about Perl6 is that it takes a different approach. Perl doesn't have a simple syntax like Smalltalk or Lisp. Instead it has a very powerful system for text manipulation that can handle the complexity of Perl's syntax. In theory, that's even more powerful than Lisp macros or Smalltalk's implemented-in-Smalltalk compiler. It'll be very interesting to see how it plays out in practice.