Communication and miscommunication are both central to Sense and Sensibility – the novel is full of moments of misunderstanding as a result of what is said (or notably not said). The characters are constantly in discourse with each other, whether in person or in letters, but that doesn't mean that they're always clear with one another. Actually, sometimes it's the surplus of language that makes things unclear – Austen shows us that more words don't necessarily help explain anything. Rather than simply talking and talking, the important thing is to make sure that you're actually understanding each other – something that our characters aren't always capable of. Sound familiar? It should, because it's frequently true in real life.
The central conflicts in Sense and Sensibility are caused by miscommunication or unclear communication; this is a symptom of a society too fixated on propriety to allow for clear and direct human interaction.
The problem of communication in Sense and Sensibility is simply one of bad authorship – not on Austen's part, but on the characters. Austen depicts a world in which none of the people she creates are able to "author" or express their own opinions clearly and concisely, as a result of their social conditioning.