The grammar says the past perfect tense expresses action in the past before another action in the past.
I had once had some thought of fixing in town myself—for I am fond of superior society; but I did not feel quite certain that the air of London would agree with Lady Lucas.’
had ...had: Past Perfect
did...feel : Simple Past tense
This is the only point, I flatter myself, on which we do not agree. I had hoped that our sentiments coincided in every particular, but I must so far differ from you as to think our two youngest daughters uncommonly foolish.’
had hoped :Past Perfect
coincided : Simple Past tense