SONAR-9352 we began ignoring QG conditions on coverage and duplications on new code when there are fewer than 20 new lines. We did this because of our own experiences with "diminishing returns" situations where the cumulative change sets were small and one or two uncovered lines caused the project to fail the QG.
However, not everyone sees this as a good thing, and it makes sense that in some industries - safety-related, E.G. - covering that single line of code is not a situation of diminishing returns, but one of absolute necessity.
We'll introduce a setting to disable this feature.
The setting can be change at instance level by an Administrator in the "General" section of the instance settings:
Quality Gate > Ignore duplication and coverage on small changes.
It can also be overridden for each project in the project settings.