D solved the problem with what happens with (a == b == c) in an unusual way. It gives an error message. Both the C way and the Python way are considered wrong. You're going to have to add ( ) to clarify.
Which makes me wonder whether they came up with this idea themselves or if they borrowed it from D.
In any case, I think that this is the only reasonable solution for new languages. Because if you go with C way it will be surprising for people who expect Python way and vice versa. So, making this syntax illegal is the only way to uphold the principle of least astonishment [1].
[0] https://play.rust-lang.org/?version=stable&mode=debug&editio...
[1] https://en.wikipedia.org/wiki/Principle_of_least_astonishmen...
When I implemented it, I had seen many knock-down drag-out debates about which was the best way to deal with it, and none of them mentioned simply making it illegal.
It was another one of those features that were based on my experience designing aircraft systems.
Another one adopted by pretty much all languages since D is the _ in numeric literals (although C++ used a backtick). It was just something that was obviously right once you saw it. But I didn't originate it, I cribbed it from Ada. I've always had a soft spot for Ada.