Earlier quoted context omitted.
Looks like HN actually uses JavaScript to indent, based on a attribute where n is the level of indentation. So it’s more a progressive enhancement than something built into the underlying HTML. ( Edit: I think my initial take above was wrong. Please see below. )
> Looks like HN actually uses JavaScript to indent I’m not an anti-JS person, but why? CSS seems so much more sensible for that.
I want to correct my initial take above. The JavaScript code I was looking at actually appears to show/hide children in threads.
The indentation appears to be handled separately by invisible GIFs: