While I was writing this post, at some point Safari stopped recognising the whole content as something it could display and instead only displayed the definition list that makes up most of the article.
Interestingly, Safari appears to do more than I expected when trying to detect if you’re reading an article. If I take the exact same markdown file and add some nonsense paragraphs to the start, outside of the definition list, the whole of the article is displayed. This tells me that instead of just examining the tags it’s actually detecting where the bulk of the content in a page is.
That generally makes sense, but it’s annoying when the majority of your article is inside another element. I think my site is readable enough without using reader to just leave it, but it’s a little something to think about.