How do subthreads work? I assume they're just hidden due to divisiveness / flamewar risk?

Mostly it's offtopicness, especially generic tangents: https://hn.algolia.com/?dateRange=all&page=0&prefix=true&sor...

Understood. Hope I didn't do anything "wrong" in this case.

Not at all! Your comment was super specifically on topic.

The generic one which I detached was https://news.ycombinator.com/item?id=24890238 - detach means it's no longer a reply to your comment but is rather a top-level comment that can therefore float to a lower location on the page.

There's nothing wrong with https://news.ycombinator.com/item?id=24890238 either. It was just more generic. Also important to understand: the moderation decision is not primarily about a comment, it's about the entire subtree. I don't want people to feel blamed for what they posted, especially when it was other commenters who ended up going further off topic.