I tend to agree. JA establishes a comic tone in her depiction of charecters like Mary.
To me, Sir Walter is a figure to be laughed at with all the mirrors and perhaps, amused outrage at his dismissal of navymen who defended the nation. Yet his snobbery and vanity which make him funny; are offered for readers' dispproval.
I think this is typical of JA's satire; I get a sense of both her detached amusement and engaged mockery. :)