I think this is why we glimpse Captain Wentworth sneering at Mary when she's being a snob and rolling his eyes at Mrs Musgrove when she's grieving her useless son. We see his humanity. His is a "frank...open-hearted..eager character" who's sincerity she can depend on because he "sometimes looked or said a careless or hasty thing"

Re-reading the novel after viewing Persuasion (2022), I was partly focused on finding the kind of comedy that Cracknell's adaptation foregrounds, which verges on slapstick at different moments, especially when Anne is involved. Anne's humor in the novel remains in the familiar realm of the satirical. But this scene with Charles Musgrove, Mary, and Anne is one of the few moments where it's possible to see some silliness in the narrative. The image of Charles chasing after this small animal to disengage himself from Mary's complaints is charming and makes him look quite silly: he is disarmed by her tenacious complaining and rather than endure them prefers to run after a small animal. The humor is turned against the couple, not at all an exemplar of marital respect. These two spouses might be found bickering but they are also conflict-averse, unable to enter into honest dialogue. The movie is inclined to giving Mary the upper hand. In the novel, Charles' possibly threatening masculinity is suggested through his persona as an avid sportsman. Hunting for weasels was not silly in and of itself at the time. These small and slender creatures had (and still do) a reputation for being ferocious predators. Thomas Bewick, who Austen would have known, describes them as follows in his A General History of Quadrupeds (1790): "The Weasel is very common, and well known in most parts of this country; is very destructive to young birds, poultry, rabbits, &c.; and is a keen devourer of eggs, which it sucks with great avidity" (219).