They are not invisible in any half-decent editor.

But in the majority of editors that actual people use (mainly, jupyter/ipython), they are invisible. Not to distract from my point though, which is that a good programming language should be easily editable from Notepad.

This is where your bias shows. You define this "majority of people" by looking at your niche - you must be in academia or big data. I can tell you that in my niche nobody knows what the hell jupyter even is, and they use real editors like PyCharm, emacs, vim and so on, where whitespace is never a problem.

> a good programming language should be easily editable from Notepad.

The '90s called, they want their notepad back. Please. Not even Windows users run Notepad, anybody with a minimum of knowledge will use Notepad++. And guess what, N++ has plenty of features to deal with whitespace.

Yeah, point taken about my bias. Dealing with python via jupyter has been my biggest source of frustration with python.

But there are still plenty of cases where you will come across python via a bad interface, such as a shell interface to a server that I haven't set up properly (I come across this a lot since I've a lot of code running in clusters), and new computers or other people's bad setups or computers.

Even when using elpy-mode in Emacs, I've had problems when I tried to tabify and untabify a file (to change indentation length), which completely changed program logic in multiple places, and resulted in subtle bugs that I caught much later.