I understand where the author is coming from and respect their contributions to Commonmark. But... There are tons of markup languages for prose that have well-defined specs. So, why did Markdown win? IMO, because it does not have a well-defined spec. It is highly tolerant of formatting errors, inconsistencies, etc. If an author makes a mistake when writing Markdown, you can always look at it in plain text. Whereas a…
Regarding the specific author's suggestions, he explicitly writes that he doesn't propose to implement them in the actual MD "standard", since backwards compatibility is more important. That said there is value in making the markup less ambiguous while preserving the "writability" even if it's just a thought experiment.