Can we say "on the brink of off-topic"?

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.

Solution 1:

Your first example is grammatically dubious (off-topic is an adjective, which is uncomfortable in the situation), but on the brink of being off-topic is unexceptionable.

The second example is interesting. I would regard on the brink of as a metaphor rather than an idiom, meaning 'one step more would fall into'. If this is right, on the brink of truth is difficult to understand; you don't stumble into telling the truth. On the brink of falsehood is clear precisely because it is possible to push the truth to the limit, and also possible to go one step too far into actual lying. But it isn't simply 'negative results only', either. Somebody may be on the brink of giving all his money to charity, or indeed on the brink of getting married. My view is that the phrase implies no more than (being close to) a sudden change, but others may see it differently.

Solution 2:

There is no restriction of 'on the brink of' to negative situations. Anything that has a perceived edge or threshold to it would work, for example, 'on the brink of success' - you're almost winning.

For your two examples, 'truth' is pretty clearly recognizable as a sharp concept, but 'off-topic' (an adjective used for a more unwieldy ('off-topicality') or blatant ('irrelevancy') noun for the concept, is a bit blurry edged. Also, 'off-topic' as a noun is somewhat informal; it sounds OK spoken but is pedantically ungrammatical (would work in People magazine but not the NYT) so maybe that's why it doesn't 'work' in your native language.

Solution 3:

if you are on the brink of sth, you are almost in a very "new", "dangerous" or "exciting" situation. In this sense, brink refers to the point beyond which an action, state, or condition is likely to begin or occur. E.g;

Scientists are on the brink of making a major new discovery.

So, as @Schroedingers Cat clearly explained, your examples will not have the sense you mention.