I wonder if the author is aware of the __VA_TAIL__ proposal[1], it covered similar grounds and IMO very well thought out, but unfortunately not accepted into C2Y (judging from committee meeting minutes).

[1] https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3307.htm

Yes, I know that it was not accepted, but do not have any color on why not. It's well thought out; but I do not think the semantics are self-evident to the average C programmer who already finds the preprocessor inscrutable.