But as I explained in my above linked comment, it’s moving the problem to the right place. For example, pre-HTML5, there should only be one H1 on a page. But the Markdown spec, which I believe we all agree should be portable and not tightly coupled to HTML, doesn’t and shouldn’t concern itself with possible collisions between a level one Markdown heading and an H1 in the embedding context. It’s the responsibility of the embedding context (e.g. this discourse page) to demote the Markdown headings if it wanted to implement the “only one H1” rule. It’s actually far more complex to try and solve this problem for every possible downstream context, both those that exist and ones that haven’t been invented yet. It’s far more complex to solve it in the wrong place.