Fanny knew her own meaning, but was no judge of her own manner. Her manner was incurably gentle; and she was not aware how much it concealed the sternness of he purpose (33.6).
People often have a hard time expressing themselves clearly in this book, and Fanny is no exception. It's notable that Fanny seems to have no control over her body language and the sort of impression she gives people.
"Certainly, my home at my uncle's brought me acquainted with a circle of admirals. Of Rears and Vices, I saw enough. Now, do not be suspecting me of a pun, I entreat."
Edmund again felt grave, and only replied "It is a noble profession" (6.49-50).
Mary is one of the few people in this book with a good sense of humor and she often delivers witty and risqué statements. Edmund appears to have had his humor gland removed and greatly contrasts to the lively Mary.
"But was there nothing in her conversation, Fanny, that struck you as not quite right?"
"Oh, yes, she ought not to have spoken of her uncle as she did. I was quite astonished. [...]."
"I thought you would be struck. It was very wrong – very indecorous" (7.4-5).
Edmund asks Fanny some very leading questions in this scene and he basically prods her into saying something that confirms his own opinions. In a lot of ways, Fanny is a reflection of Edmund.
Lady Bertram constantly declined it; but her placid manner of refusal made Mrs. Rushworth still think she wished to come, till Mrs. Norris's more numerous words and louder tone convinced her of the truth (8.2).
Fanny isn't the only one who has trouble making her meaning clear. The passive Lady Bertram also confuses people with her manner and the book seems to suggest that speaking more actively (like the loud Mrs. Norris) is a more effective way of communicating.
"Poor William! He has met with a great kindness from the chaplain of the Antwerp," was a tender apostrophe of Fanny's, very much to the purpose of her own feelings, if not of the conversation (11.26).
Fanny has a definite streak of self-absorption, as this scene reveals. Rather than listen to those around her and actively participate in a conversation, Fanny is off in her own world and comments on her own private feelings.
Fanny could have said a great deal, but it was safer to say nothing, and leave untouched all Miss Crawford's resources [...] lest it should betray her into any observations seemingly unhandsome (21.17).
Fanny equates silence with safety and seems to find action and speaking risky. But even though Fanny protects her secret love of Edmund through her silence, she opens herself up to being misunderstood by staying silent all the time. People have to make their own assumptions about her since she gives them nothing to work with.
[Miss Crawford] was determined to see Fanny alone, and therefore said to her tolerably soon, in a low voice, "I must speak to you for a few minutes somewhere"; words that Fanny felt all over her, in all her pulses and all her nerves (36.5).
The detail here of Fanny's "pulses" and "nerves" helps make a thematic statement on the power of words and language. Speech can have a very strong physical effect on people, and the sensitive Fanny often "feels" words very strongly.
Had she ever given way to bursts of delight, it must have been then, for she was delighted, but her happiness was of a quiet, deep, heart-swelling sort; and though never a great talker, she was always more inclined to silence when feeing most strongly (37.6).
Silence plays as important a role as speech in this book, and it's notable that Fanny's feelings often can't be expressed or translated into words. Language tends to fall short for Fanny, and her silences are often more expressive than people realize.
Mr. Rushworth hardly knew what to do with so much meaning; but by looking, as he really felt, most exceedingly pleased with Sir Thomas's good opinion, and saying scarcely anything, he did his best towards preserving that good opinion for a little longer (19.36).
The power of silence emerges again, though in a much more humorous way. The foolish Mr. Rushworth demonstrates the old maxim about not having anything good (or in this case, intelligent) to say. Mr. Rushworth keeps his mouth shut and doesn't ruin Sir Thomas's opinion of him by saying something dumb.
[B]ut Mr. Yates, without discernment to catch Sir Thomas's meaning, or diffidence, or delicacy, or discretion enough to allow him to lead the discourse while he mingled among the others with the least obtrusiveness himself, would keep him on the topic of the theatre [...] (19.26).
Communication in Mansfield Park is as much about listening and responding to others as it is about speaking and expressing yourself. Mr. Yates is oblivious to the people around him and ends up shooting his mouth off inappropriately.
"Is there not something wanted, Miss Price, in our language – a something between compliments and – and love – to suit the sort of friendly acquaintance we have had together?" (29.23).
Once again, the idea of language often being inadequate emerges. Mary wants a word to express herself, which contrasts with Fanny, who often does away with language all together in favor of silence.
William was often called on by his uncle to be the talker. His recitals were amusing in themselves to Sir Thomas, but the chief object in seeking them was to understand the reciter, to know the young man by his histories; and he listened to his clear, simple, spirited details with full satisfaction – seeing in them the proof of good principles [...] (24.21).
Speaking, when done well, is still one of the best ways a character can express himself and help others understand him. Unlike his sister, William can successfully talk with and give other people a good view of his character.