Thank you @DesdamonasHandkerchief for all the info and for hosting! I agree this was a brilliant read. I was kind of dreading reading the last section because I remembered Sydney Carton's death (from the first time I read the novel many years ago), but I had completely forgotten the story of the evil Evremonde brothers and the rape of the peasant girl, and Mme Defarge turning out to be the sister of the dead girl... it was all very gripping and I enjoyed the last section far more than I expected! There were so many different threads coming together, it was very satisfying.
The whole story recounted in Dr Manette's long letter is insanely Gothic, it's so dark and melodramatic, but I'm fond of Gothic literature! Good point Desdamona about the implausibility of the evil brothers taking the trouble to get the girl a doctor in the first place. The notes in my edition talked about 'le droit de seigneur' (the idea that a lord from the Middle Ages onward had the right to have sex with young women on his estate, especially on their wedding night) and said it was more of a myth than historical fact. Of course, in the story of the dying peasant brother, his sister isn't actually raped on her wedding night, but he refers to the 'shameful rights' of nobles, so it seems to be an allusion to 'droit de seigneur'. Yet even if 'droit de seigneur' isn't historical fact, it seems that Dickens is using the story of the girl's abduction and rape (combined with the additional grisly elements of the torture of her husband and murder of her brother) to symbolise the bigger picture of aristocratic atrocities toward peasants and the lower classes.
I agree too that there are too many coincidences! Uncanny doubling is another feature of Gothic novels though, and all these sets of doubles are exciting: Darnay and Carton, the twin Evremonde brothers, Mme Defarge and her martyred sister, the steadfast Mrs Pross and her nefarious brother.
To me the novel is very interesting from the point of view of trauma, and how different characters exhibit symptoms of trauma. Dr Manette's loss of memory and return to his shoemaking state happens twice in the novel, when a fresh reminder of trauma becomes too much for him to handle. But there is also the sinister repeated words of the dying peasant girl, as she names her family members and counts to twelve. It's fascinating that Dickens gives Mme Defarge a back story that makes her a victim of trauma as well; in her case, she handles the trauma by becoming a kind of abuser herself.
And these individual familial traumas are all part of the much larger historical trauma that France is going through.
Freud wrote a famous essay on trauma called 'Repeating, remembering and working through', where he argues that until you've actually managed to 'work through' a trauma, you're condemned to just keep re-enacting it - you're still 'trapped' in the original event as it were. Dr Manette eventually manages to work through his trauma with the support of his family, but the peasant girl dies in her traumatised state, and her sister (Mme Defarge) keeps perpetrating the violence until she too is killed.
I should say I'm not a Freudian, but some of his ideas are interesting!
It is moving that it is such a damaged person (Sydney Carton), as you say @LadybirdDaphne , who becomes the bringer of redemption in the novel.