Obsessions, fixations, and affectations --- I've got 'em aplenty, particularly when it comes to stylistic conventions in writing. And like the fellow who was surprised to find he had been speaking in prose all his life, I only learned yesterday that there's a term for the comma that I habitually put before the conjunction in a list of three or more items. It's called the "Oxford Comma", or sometimes the "Harvard Comma". The style guides of those antique institutions mandate it.
I use the Oxford Comma because it's logically consistent and reduces ambiguity. (There are a host of funny parsing mistakes that can occur without it.) The same holds for putting punctuation outside quotation marks when that punctuation doesn't really belong to the quoted words. Yep, it's a Briticism, but it's also the most reasonable way to convey information with accuracy.
A quick string search through the ^zhurnal finds that the characters ", and" occur at least once on more than 1,000 of my entries. Looking at a sample of them in detail finds that the majority do exhibit the Oxford Comma. A similar search finds periods outside of quotes in several hundred instances, and likewise for commas outside quotes.
At least I'm (occasionally) consistent in my idiosyncracies!
In the AP Stylebook, it was referred to as a 'serial comma' (and may be referred to as that in other references. Makes a world of difference when you write about buying "color, black, and white TVs."