As a professor at the University of Delaware, I read a lot of writing by college students, and in it a strong recent trend is reversion to comma-by-sound. I attribute this not so much to students’ love of the Constitution and the classics but to the fact that they don’t read much edited prose (as opposed to Facebook status updates, tweets and the like). Two things that you really need to read a lot to understand are punctuation and spelling. (Not coincidentally, spelling is the other contemporary writing disaster.)One of my work tasks is to edit memoranda (often lengthy documents) of case fact and analysis that will ultimately be read by Commissioners and their advisors. Most people can write fairly coherently, so I spend time fine-tuning grammar, punctuation, and the like. It turns out that even well-educated people have all sorts of trouble with commas (and, worse, semicolons), to the point where I sometimes suspect people of randomly inserting commas.
As far as comma use goes, my students play it by ear. I see this most dramatically in sentences that start with conjunctions like “And,” “But” and “So.” (Your junior high school English teacher may have told you never to start a sentence with a conjunction. To the extent that was once true, it isn’t anymore.) So students will write sentences like this:
So, students will write sentences like this.
But, they are wrong.
You see this kind of thing all over the Internet as well. People punctuate that way because, if they spoke these sentences, they’d pause after the conjunction (and because the extremely fanciful and undependable Microsoft Word grammar and style checker refrains from applying a squiggly green underline).
It's good to know that there are others out there continuing to fight the good fight.