When I worked in python I made this exact mistake monthly.

How, though? Every code editor I've used supports holding indentation at a certain level until you change it, so if you write:

  if foo:
      bar()

and hit enter after the "bar()", it would drop you down so that the next thing you type would be under the "b". It's not really different from using curly brackets from the perspective of typing in code.

Cut and pasting code to move it around. Every editor was just slightly jittery about keeping the indentation levels consistent.

Completely agree, this is a common argument ever since Python existed. I've also used it for almost 25 years and these kind of indentation errors just don't happen. I see it the same as forgetting closing brace. Python programming writing C code might forget it initially, but C programmer absolutely will not forget it, it's in their muscle memory. And the same applies for dealing with indentation.