Of course I can imagine grammar without punctuation, but we have become hooked on writing and it has come to affect our speech. Just as any Western melody from Bach to pop 'implies' a sequence of chords, anything we say implies its written appearance.

Just because the punctuation only adds convenience, I don't find that it follows that it is not an integral part of our grammatical constructions. This sentence implies a semicolon after its ninth word it looks odd without it. It would be worse if we did away with full stops and capitals; the grammar could be otherwise perfect but confusion would surely set in.