How we cite our quotes: (Part.Letter.Paragraph)
Quote #7
With Danceny himself I have often, in spite of myself, felt a certain constraint which prevented my telling him all of my thoughts. (2.75.4)
Cécile and Danceny have horrible communication skills—with each other, at any rate. They don't intend to deceive one another, usually, but they're not fully honest, either. They're communication isn't the calculated performance we see in Valmont and Merteuil's letters. It's more of an explosion of their fears and hopes and dreams. Cécile holds back because she doesn't trust herself not to spill her guts.
Quote #8
This perpetual harping on the same string, which I already find comes something short of the irresistibly amusing, must be exceedingly insipid to anyone who is not personally concerned. (2.76.20)
This line almost functions as an "aside" to the audience. None of us reading this novel are personally involved with the characters, and yet the author, Choderlos de Laclos, surely hopes his readers don't find the correspondence to be exceedingly insipid (bland, drab, boring).
Quote #9
This is what comes from using language which nowadays is so abused that it means even less than the jargon on compliment. It has become no more than a set of formulas, and one believes in it no more than one believes in 'your very humble servant'. (3.121.2)
The Marquise wants Danceny to write what he means—what he thinks and feels—not with flowery prose filled with clichés. Of course, she wants to know what he thinks and feels so she can manipulate him more easily. However, she can't give any indication of that, so she couches it as a stylistic point about the effective use of words.