High and Low
Whenever we read Hardy's narrator, we tend to encounter a lot of proper, formal language. But Hardy creates a really sharp contrast to this formality by also giving us a bunch of dialogue spoken in the 19th century equivalent of Good Ol' Boy lingo.
You can see this contrast clearly in passages where the two styles are plunked down beside one another, like at the end of the book:
"Then Oak laughed, and Bathsheba smiled, for she never laughed readily now; and their friends turned to go.
'Yes, I suppose that's the size o't,' said Joseph Poorgrass with a cheerful sigh as they moved away; 'and I wish him joy o'her […]'" (57.51-52).
In the first line, you can clearly see one style, and in the second, you can see the countrified language of Joseph Poorgrass. This mixture of styles helps us keep track of the class of the characters. In a perfect world, a character's class would have no bearing on what occurred to that character, but Victorian England was not a perfect world. A character's class determined their station in life, their marriage prospects (think of Gabriel Oak and his failed proposal to Bathsheba) and a whole slew of other details.