I agree Darcy’s need to redeem his character before Lizzy is a matter of honor to him. I also agree the accusations against him about Wickham are greater in magnitude than those of separating Bingley and Jane but IMO he dismisses the second too readily still. Darcy was perfectly correct in his actions towards Wickham and needs only explain what “really” happened, he has the Colonel as a witness after all but he was not so correct in separating Bingley from Jane so his actions in that situation are questionable. I do not think he gives the Bingley—Jane situation enough thought because he does not follow though honorably. IMO it is not wrong to advise a friend if you believe he is making a mistake so on that account I have no quarrel with Darcy but he has his facts wrong and he then uses “arts” to assure they remain separated.

But I have other provocations. You know I have. Had not my own feelings decided against you -- had they been indifferent, or had they even been favourable, do you think that any consideration would tempt me to accept the man who has been the means of ruining, perhaps for ever, the happiness of a most beloved sister?" (Chapter 34)

In his letter, Darcy shows considerable care of Georgiana’s feelings as he should and blames Wickham that she was hurt but he is spectacularly unconcerned about Jane’s feelings although she suffers at his hands. Darcy wrongs Jane twice, first by persuading Bingley she did not care for him and second by concealing her presence in town from him. Darcy’s honor demands an admission of guilt for his concealment of Jane because by his standards the act of subterfuge is dishonorable in itself. When Darcy finds out Jane had regard for Bingley it becomes apparent his successful persuasion of him is based on an unintentional lie. However, Darcy claims he was right to have separated them due to the impropriety and bad connections of her family but he is well aware that is not why Bingley caved in to persuasion; he gave in because he believed Darcy’s judgment that Jane was indifferent to him. It seems to me the honorable thing for Darcy to do now is to tell Bingley the truth but his claim of “it was done for the best” suggest he intends to withhold the truth from his friend. Darcy is not thinking this situation through very clearly. I think withholding the truth about Jane’s regard now is just as dishonorable, perhaps more so, than withholding the information she was in town because by doing so Darcy is perpetuating the lie, assuring Jane’s unhappiness continues and allows his friend to be the instrument of it without his knowledge.

If I have wounded your sister's feelings, it was unknowingly done; and though the motives which governed me may to you very naturally appear insufficient, I have not yet learnt to condemn them. (Chapter 35)