Alright. Point by point (although I'm considering both the beginner and "advanced" arguments for each point simultaneously):
> You Should Be Able to Run 2 and 3
That makes no sense. The whole point of versions is that they are different. Maybe he means 3 should be backwards compatible. That is potentially valid criticism. That said, AFAICT, the breaking changes are pretty reasonable [0][1]. Also, I'm not sure what world he is living in, but interop between Java and C/C++ through the JNI is not easy. As a math major I'm not sure what the "solid math" here is. I think it is ironic that the CLR is referenced here so extensively - it has made some pretty big breaking changes in the past (unlike Java, it decided to break backwards compatibility to have reified generics).
> No Working Translator
Translation is tough, _especially_ in languages like Python that don't have good static guarantees. The real problem here is probably that the code you want to produce with a translator should look as much like the original code when possible. That _is_ tough. The point is it isn't just what the program does in terms of inputs and outputs that you want to preserve. You still want it to look more or less the same.
> Difficult To Use Strings
This is not an incorrect point. I think Python 3 wanted to have both the performance of byte strings and utf8-by-default strings (finally!). The intention behind that seems reasonable. As a proponent of strong static typing, the error message he shows seems quite benign. That said, I understand how one might be unhappy about this.
> Core Libraries Not Updated
This may be the case, I'll defer to someone else. That said, this is yet another claim the author makes without much backing (this alone could be the subject of a blog post given the right backing). The quip about the Python community liking bad design seems a bit gratuitous.
[0]: https://docs.python.org/3/whatsnew/3.0.html
[1]: http://sebastianraschka.com/Articles/2014_python_2_3_key_dif...