Persuasion is a departure from the other novels in several ways---it's more poetic, uses the rhythms of time to explore feelings, and is more in tune with nature, just to name a few, as well as the use of structure and punctuation to highlight emotion as described in your post.

Like you and others here, I've also felt a distinct difference in the tone and style of this particular novel. I was reading an essay this summer (A. Walton Litz, Persuasion: Forms of Estrangement) which led me down the same path as you, how JA makes her words do double duty. Litz used a different section of the text to make his point:

"...'free, indirect speech,' in which lengthy dialogue is compressed and located within the central consciousness, is combined with more conventional narrative methods to give a sense of the entire novel taking place within the mind of the heroine... Another aspect of style in Persuasion...is the rapid and nervous syntax designed to imitate the bombardment of impressions upon the mind. A fine example occurs when Anne, a victim of the rambunctious child Walter is rescued by Captain Wentworth.

In another moment, however, she found herself in the state of being released from him; some one was taking him from her, though he had bent down her head so much, that his little sturdy hands were unfastened from around her neck, and he was resolutely borne away, before she knew that Captain Wentworth had done it.

Here the passive construction, the indefinite pronouns, and the staccato syntax all imitate the effect of the incident upon Anne's mind."

He does kind of throw a wrench into it for me though by stating that "The sentences of Persuasion do, for the most part, move away from the Johnsonian norm but cautions that "The printer of Jane Austen's day had great license with punctuation, paragraphing, and even sentence structure, and part of the 'flowing' quality of Persuasion may derive from a printer (T. Dawson) whose standards and tastes differed from those of the printers who handled the earlier manuscripts." I understand what he's saying but I like to believe that JA's is the heavier pen.

Just have to say that the entire scene with baby Walter is one of my favorites and his removal by the Captain is so wonderful. Just imagine if they had exchanged the Bath Marathon for this scene in the last adaptation...