The point that Marxists should get from _Mansfield Park_ is that the Crawfords and Fanny Price/Edmund Bertram, liberalism and conservatism, are evil dialectical twins. Fanny Price, however, has no better choice -- certainly no socialist choice -- in that she is a woman of the early nineteenth century, unlike us. More than any other work by Jane Austen, _Mansfield Park_ allows us to see the horrors of dependence for a poor woman under capitalism, making clear that horrors lie _not_ in dependence as such _but_ in the nature of dependence shaped by sexism & class oppression; Austen could not see any alternative to Fanny's choice -- hence the novel's melancholy tone. (Edward Said says that Austen neglects to take a critical look at the British Empire, though she does make clear that Mansfield Park is dependent upon the plantations in Antigua.) One can't anachronistically fault the novel for not being a socialist & dependency-theorist treatise ahead of time, though. That Austen, while embracing the conservative order, nonetheless did not shy away from portraying in telling details the problems of capitalist society in _Mansfield Park_ is what is valuable for us. Oftentimes, conservatives in the past were better able to see the problems of capitalism & the ideology of individualism it entails than liberals. Today, we have no "conservative" in the true sense of the word, for everyone is committed to "improvement" -- environmentalist sentiments found here and there notwithstanding.
The point that Rob & Carrol have made is that capitalism & sexism make the biologically & socially necessary interdependence of human beings poisonous. (Carrol further argues that the drive inherent in M-C-M' is allegorically figured by Mrs. Norris -- a debatable position as Rob suggests, but an intriguing take that can be fleshed out).
Human beings will perish if we are to try to live like Rousseau's savages who only existed in his heuristic state of nature.
Yoshie