You are right about that. I mean, if his character had not needed justice then he never would have written to Lizzy in the first place. Darcy could have added an apology for his ungentlemanlike proposal or a sorry for the suffering Jane has gone though but he does not. The letter unlike the rejection does not have to be all about him.

I agree business letters could be exchanged openly without consequence but Darcy’s letter does not seem like business to me at all. It is all about personal justification of his actions in personal matters and the giving and accepting of the letter is done in secret. If anyone witnessed the exchange I do not think they would assume Mr. Darcy of Pemberley had business with Miss Elizabeth Bennet that was not of a personal nature. The first subject in Darcy’s letter is his rejected offer to Lizzy. He then discusses both Jane & Bingley, helping to separating them, Wickham and his father and the living, then the foiled elopement of Georgiana and Wickham, lastly raising Col Fitzwilliam as a witness. I would agree that the letter falls short of my idea of a love letter but it is personal not business IMO. ;D