The Return of the Native begins with some seriously old-fashioned communication techniques: signal fires. The communication strategy of choice for desert island castaways (like in Pirates of the Caribbean) and Middle-earth denizens trying to rally the troops (think The Return of the King). So what's with the use of signal fires in The Return of the Native? There's nothing epic going on as far as we can tell. Well, kicking off the book with signal fires and practically no dialogue for the first few chapters really helps to set the tone for the rest of it, which is often light on dialogue as well. Communication, when it occurs at all, is often unspoken and is heavily reliant on actions, interpretations, silences, and symbols. Objects often speak louder than actions and words here – see Mrs. Yeobright's reaction to seeing Clym's boots by his door, or Diggory's response to Thomasin's glove. These objects convey more meaning than a lengthy conversation could to these characters.
But when people do decide to start speaking, it's often astonishingly blunt and eloquent. The conversations in this book even border on theatrical – people speechify and deliver monologues and have very snappy dialogue. Yet no one seems to really hear anyone else when they speak – characters often speak at one another and not with one another. See Eustacia and Clym's courtship conversations, in which neither seems to really register what the other is saying. All communication boils down to subjective interpretation, which of course means that people have more than their share of misunderstandings. So it's really fitting that the novel concludes with Clym as a poor preacher who mainly talks to himself.
Non-verbal communication plays a more important role than verbal communication in this novel.
The letters that Clym never writes to his mother or sends to Eustacia epitomize the major flaws of Clym's character and the major theme of the book: miscommunication.