Then maybe the statement should have been "I believe it is basically impossible for Python to win back all that performance loss without adopting radical and jarring features like dropping the legacy C interface to Python objects."

The fastest dynamic languages I see are those which have no C interface at all. How many of the performance optimizations in a modern JavaScript engine would be possible if it had to support accessing every property of every object as a C string at any point in a program? JS has exactly none of the features that comment claims would be necessary for performance.