My knowledge of Alexandrines, whether Racine's or anyone else's can be written on a rice-grain, but it is a lovely comparison nonetheless, and I thank you, Lief, for bringing it to our attention. I am quite sure that JA's prose was developed by the habit of reading aloud- it is one of my pet theories that she wrote with precisely that in mind. Music, too had a great deal to do with it, I am sure. P&P starts at a gallop,and continues at breakneck speed for the whole of book one- like a merry dance, or rippling scales. S&S is a slower measure, a little more sedate in the speech of Elinor and, rhythmically swinging with Marianne.
I find one more influence, too, especially in Persuasion ,and MP, and that is the rhythms and alliteration very reminiscent of the Book of Commmon Prayer. None f the biographers really want to touch that one, although Irene Collins does mention it in passing with reference to JA's own prayers and verses.