The textworkers in the Greco-Roman tradition, who guarded, preserved, transmitted, and explained their canonical texts needed a reason (or at least a justification) to interfere in the texts that they considered foundational, important, and in principle models of correctness and clarity.
In the framework of the Working Group "The Learned Practices of Canonical Texts," Ineke Sluiter argued that they use the concept of "obscurity" for this purpose, as a diagnostic tool that leads up to and justifies a variety of textual and exegetical practices. Depending on the nature of the obscurity, they will move on to the elucidation of a difficult or obsolete word, explaining the construction of a sentence, providing little-known background information, explaining the true or underlying meaning of text elements (from etymologies of one word to figurative readings of one or more words to wholesale allegoresis), emending the text, or declaring it spurious.
Since "clarity" was an important cultural and rhetorical norm, exegetes would often consider obscurity something of an embarrassment, itself in need of explanation. They distinguished intentional and non-intentional obscurity, and each form could either be bad (if the result of incompetence or pedantry) or justifiable (for reasons of style, pedagogy, safety, etc.).
The paper also touched on the tolerance for obscurity that marks the reception of foundational texts, in line with modern ideas on pragmatics and communication.