>There is nothing harder to understand about indentation levels than curly braces //
At the start of this year I finished a first course in Python to learn in anticipation of [possibly] using it for home learning with my kids (it seems widely used for education). As I'm familiar with programming I searched for an IDE as I started. It told me when I had dropped a space or used a tab by accident. I tried several different environments including my standard editor choices - nano and Kate - revealing non-printing characters was a clear advantage. Others (primarily adults) who were starting fresh in programming had lots of problems with errant spaces.
With braces you can see more clearly when there is an error of addition or omission, not so much with spaces. Like I tried to say above: this is clearly tractable with the right tools but the demarcation - I feel - of braces can be a more clear and obvious sign of separation than whitespace. For younger people with less spatial reasoning and less accurate perception of text lining up it rather seems it could be pretty much harder to use whitespace structuring.
Personally I like the overall "clean" appearance of Python compared to PHP (say), debugging with tools is fine, when I was testing different environments and tripped on whitespace problems it was a nightmare rather reminiscent of trying to debug HTML tables some years back.