HTML is a terrible authoring format. CSS is a terrible everything. If you want something to last, the thing that will last is the human-created source - probably markdown. I'm not worried about my blog posts sitting in their git repository being lost. The Jekyll pipeline that adds a Javascript header/footer might go away, as might the Javascript that pretifies my raw posts, but the markdown is durable, and a future a…
No, I trust HTML and CSS to stand the test of time far more than Markdown. Do you know how many different variants of Markdown there are, how they affect the interpretation and appearance of the content, how they can break surprisingly much? And when it comes down to it, as soon as you want to do anything even remotely interesting in Markdown, you have to drop straight HTML in there, and pray that the Markdown engine…
One plus a bunch of non-standard extensions. Do you know how many different variants of HTML there are, how rare it is for real-world HTML to actually conform to any of them, and how many different interpretations of that there are. (To say nothing of CSS, the standard so complex that it's never actually been implemented).
> And when it comes down to it, as soon as you want to do anything even remotely interesting in Markdown, you have to drop straight HTML in there
Just say no. If your goal is writing something intended to last, you should be able to convey it in mostly-plain text.