1 Cor 4:6 is a favorite verse for the WT. They of course have extended the application to include not just the Bible but also the rulebooks and written interpretations that they have produced. I myself have been suspiciously viewed when referring to older publications that the local Elders were unfamiliar with, being reminded not to "go beyond what is written". Even here we have used the verse to condemn the WT's practice of adding rules and volumes of interpretation to the Bible textsas "going beyond what is written" usuallly meaning the Bible. However a cursory check with online Bible translations reveals that the verse is not easily translated nor understood. Here's why. The phrase "don't go above the line" was inserted by a translator as an instruction to someone in the translation process!! The effort to make this copyist note fit the larger sentence has been clever and creative.
Some translations have even dropped the phrase from the text.
The verse reads much better without the inclusion. Ironically the writer was insisting that Christians not judge others as much remained secret to human eyes not to be scrutinizing others suspicious of an "independent spirit".