From the Quotation of the day mailing list, 2017-05-17:
"He uses commas grammatically. I deploy them musically." -- Toni Morrison, writer, on her disputes over the use of commas with her editor Robert Gottlieb.
(submitted to the mailing list by Terry Labach)
[If I understand correctly, when punctuation marks were first introduced they were for indicating pauses of different lengths when reading aloud, and grammatical use came later.]