Over the course of the long eighteenth century, a distinct Southern Dutch linguistic identity emerged in the region now known as Flanders, and spelling features are at the heart of this developing linguistic autonomy. By analyzing eighteenth- and early-nineteenth-century normative and metalinguistic comments about three highly salient spelling variables (the spelling of the long vowels a and u in closed syllables, the ending 〈-n〉 or 〈-ø〉 in masculine adnominals, and the orthographic representation of etymologically different e and o sounds), this paper will show how seemingly insignificant features increasingly came to be portrayed as representing an unbridgeable linguistic gap between the Northern and Southern Low Countries. At the time of the political reunion of both parts of the Dutch speaking territories (1815–1830), this perceived gap then gave rise to different voices rejecting or embracing these shibboleths of linguistic ‘Southernness’, indicating how spelling features came to represent conflicting identities.