9 years ago, separation of presentation and content was already considered a good practice. Yet here we are with application frameworks and component-based designs that throw it all out the window...
To expect any consistent design principles on a development medium as ad-hoc and devoid of principles as the web, is wishful thinking.
HN isn't about using good practices. It's about getting to the heart of the matter. Content is content, who cares how it's displayed, for better or worse. But people keep showing up. So it must be working just fine. If it ain't broke, don't fix it.
To expect any consistent design principles on a development medium as ad-hoc and devoid of principles as the web, is wishful thinking.