It strikes me that if you used "though" instead of "but" nobody would remark on the construction. Since the two words are sometimes interchangeable when used at the start of a phrase it's not too hard to imagine somebody substituting "but" for "though" at the end of it. Follow?
Here's the putative evolution:
I don't like caramel, though chocolate's not bad.
I don't like caramel, but chocolate's not bad.
I don't like chocolate; caramel's not bad, though.
I don't like chocolate; caramel's not bad, but.
Presumably a few people think this sounds cute, the fad takes off and a new mannerism is born. Too far-fetched?
BTW I presume that saying "chocolate's not bad, though" is also anastrophe? If so, I'm thrilled to know that all my life I have been using such lah-di-dah grammatical constructions. [emoticon of a kugel preening]
On second thoughts it does rather take the gilt off it to know that millions of Ozzies are using it too - and more imaginatively!
