One of my go-to examples of high-context is The Wire's "fuck" scene. Two professionals in perfect sync investigate a murder scene. The communications themselves are not very important because they are relying on a high level of context -- they already have familiarity with the case and with each other.
On the other side of the spectrum, think about any episode of CSI or NCIS where the characters narrate everything they do and think to each other. It's necessary exposition for the viewer, and perhaps in a real-life setting collaborating in this way keeps everybody on the same page. It isn't bad at all, it is just a lower context mode of communicating.
Because GP was discussing a socially sensitive topic, but the other person asked for an explanation about an easily googleable concept. This is intentional noodle-braining, explanation on reddit: https://old.reddit.com/r/TwoXChromosomes/comments/ixp19i/did...
Often it's pretty straight forward when you ask yourself the question.
As all cultural phenomenon, there is a strong local component to it but there are still many variations : knowing where they are from, whether they grow up in big city or small rural areas, is often a good starting guess. But after a few sentences exchange showing how direct or considerate of your specificity they are, how they value your time, you usually know without doubt.
It's just about making sure you are in the right communication mode with the right person.
To bring it back to the article theme :
The way people hear a no is also pretty characteristic. So listening to their reaction when you are telling them no is also a pretty strong signal.
For example if you tell no without justification to someone from high context culture when he asked something (if he ask it probably means that from his point of view he is expecting a positive answer) he won't probably take it good. And you have a few second to come-up with a sensible reason if you don't want to ruin the relationship.
Whereas someone from low context culture is usually more direct and the no carries less weight to give or take, as in their eyes it means they will just ask to the next person.