Another difference between Darcy and the Bingley sisters is that Darcy really had Bingley's best interests at heart. He genuinely believed that Jane did not love Bingley.
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Your sister I also watched. -- Her look and manners were open, cheerful, and engaging as ever, but without any symptom of peculiar regard, and I remained convinced from the evening's scrutiny, that though she received his attentions with pleasure, she did not invite them by any participation of sentiment. -- If you have not been mistaken here, I must have been in an error. Your superior knowledge of your sister must make the latter probable. -- If it be so, if I have been misled by such error, to inflict pain on her, your resentment has not been unreasonable. But I shall not scruple to assert that the serenity of your sister's countenance and air was such as might have given the most acute observer a conviction that, however amiable her temper, her heart was not likely to be easily touched. -- That I was desirous of believing her indifferent is certain, -- but I will venture to say that my investigations and decisions are not usually influenced by my hopes or fears.
Also I think that it is a credit to Darcy that he saw Bingley as a possible match for Georgiana. It demonstrates that he was more interested in the character and temperament of her future husband than his status. While Bingley is an acceptable match, with her connections and dowry she could definitely have aspired to a 'better' match.
From the information available to him, Darcy genuinely believed his friend was about to marry a woman who didn't love him, had no connections, who had a family that left a lot to be desired and that could have cost him a lot of money to support in the future. Darcy would not have been able to call himself a friend if he hadn't made an effort to point that out to Bingley.
Darcy is no saint but he does acknowledge his mistake and he genuinely believed his motives were for the best. He also takes steps to remedy his mistake, even though it takes a few months.
I am not saying that Caroline and Louisa did not care for their brother but their motives appear to be based more on the the importance of status and connections than their brothers feelings and also Carolines jealousy of the attention Darcy has been paying E. We don't get a lot of insight into their reasoning but they definitely knew Jane better than Darcy and had spent more time with her. They also pretended to be her friend and then dropped all connection when it suited their purpose.
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When breakfast was over, they were joined by the sisters, and Elizabeth began to like them herself, when she saw how much affection and solicitude they shewed for Jane.
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their indifference towards Jane, when not immediately before them, restored Elizabeth to the enjoyment of all her original dislike.
JA does set us up to think less of the Bingley sisters.
Darcy definitely does not disguise his true feelings or pretend to think more of you than he does.
