Aside from significant whitespace (which I suppose takes a little getting used to), is there anything that marks out Python's syntax as particularly rigid compared to other languages?

I'm struggling to understand what the author is trying to argue here.

> Aside from significant whitespace (which I suppose takes a little getting used to),

If Python's whitespace takes getting used to, then you're probably poorly formatting your code to begin with.

One thing I do find mildly annoying about the whitespace is that you can't jump to the end of a block with e.g. % in Vi (goes to the matching bracket). Not a huge deal but something I notice.

This is jarring to me. Does the author use Lisp, APL, Forth or what?

I can't help but imagine someone who writes PHP without using any indentation.

well, Lisp doesn't have that much syntax. Also Brainf*ck is famously syntactically light.

Are they coding in Notepad.exe?