@cnx Grammar is about spoken language, it's about how words come together to create sentences with meaning.
Punctuation is part of writing, not spoken language. It's like spelling, which is also not grammar & only applies to written language. It's a set of conventions for how to record and transmit aspects of the spoken language using symbols.
It's good to recall that the spoken language comes first & is much older than writing. Grammar has existed for much longer than punctuation or spelling.