It’s strange that Reginald is surprised at Lady Susan’s response—he should know by now that she’ll try to spin the situation in her favor. Again, it’s also odd that he mentions her affair with Mr. Manwaring as though it’s a total shock. It’s true that he thought Lady Susan was innocent, but this was a well-known rumor, and he once believed it was true. It’s also surprising that no one questioned why Lady Susan was writing to Mrs. Manwaring—even Catherine believed this lie earlier in the novella. It seems obvious that Reginald
was, to some extent, willfully deceiving himself; he wouldn’t be this surprised otherwise. Meanwhile, the end of Reginald’s letter presents a double standard: he’s sad for Mrs. Manwaring, who is powerless to change her situation (divorce was almost unheard of in 18th-century Britain). But he also paints Lady Susan as a villain who overpowered him. He doesn’t seem to realize that, apart from her skill at lying, Lady Susan is no different from Mrs. Manwaring. She, too, had no power in her marriage to her husband, and she was dependent on Charles’s hospitality for as long as Reginald knew her. Reginald is more powerful than both women, but he still paints himself as Lady Susan’s victim. It’s true that she was always trying to manipulate him, but it’s also true that his “weakness” was an illusion. In reality, he held all the cards.