If you program in a language with a extensible syntax, such as XML in XSLT or S-expressions in Common Lisp, Scheme, arc, etc., you never run into the problems we see above in Ruby.
That's technically true. Those syntaxes have other problems.
I agree that certain syntax decisions preclude certain growth possibilities (you may recall that I believe Python's whitespace problem is vertical, not horizontal), but S-expressions aren't magic pixie dust to sprinkle around your language to make it perfectly usable and free of all syntax-related problems. The standard argument is that you should use tools to handle all of the curvy or pointy symbols, but if you only ever interact with a programming language via tools, does the internal representation really matter? Why flatten your tree into a two-dimensional textual representation form when you can keep it around in a tree? Note that Smalltalk's not in Joseph's list; it might overshadow the other languages mentioned in terms of human friendliness and power.
How interesting that the sentence "Programs should be written for people to read, and only incidentally for machines to execute." doesn't follow SICP's own blessed
(verb noun adjective) form.