I think @notriddle’s point is that it’s useful to have HTML available for when extensions aren’t available. We could add class=next to a document with consistent attribute syntax using [next](page2.html){ class: next } or similar, but GitHub does not support this extension and may not ever, so the { class: next } part is going be included in the output which looks bad. With raw HTML, GitHub will strip away the class attribute. It’s a form of progressive enhancement. If HTML was disabled entirely, then a link with a class attribute couldn’t be added to the source document at all. Links could only be added with Markdown syntax, e.g. [next](page2.html) which cannot have a class attribute.
1 Like