I'm not so sure. It's definitely the de facto standard, but I suspect minimal HTML is better. Just enough tags to add structure and meaning (H1-H6, p, a, em, section for structure including nesting, maybe more). LLMs were trained on a lot of HTML, they're good at processing it. HTML requires more tokens than markdown but I believe it's worth it. I'll find out in a few weeks as I experiment with both.