I recently learned on the brink in context of to teeter on the brink of disaster.
Now, when I want to mention that something is marginal or borderline I remember on the brink.
This question is on the brink of off-topic.
The testimony is on the brink of truth.
Are these acceptable, or does on the brink only refer to negative circumstances?
Note: The latter example works very well in my native language whereas the first one is awkward.