the "an extension to HTML" part was too long for the submision, that's why I added the "is/as" part, to make it clear that it wasn't HTML itself.
That does not really clarify your true meaning.
And a modification would have fit as a title, HN will allow a title of this length:
"Turning HTML Into A Programming Language With an Extension"
You're full title: HTML Is A Programming Language: An extension to HTML to end the eternal discusion
That was, literally, 1 single character over the HN limit. I'm sure you can have figured one out-- I included a colon when I tested it, that's an easy candidate to leave off.
Sure it's not as nice of a soundbite for posting here or your tweet, but it's accurate. I think most of us here will at least scan a title, but often get annoyed when it runs up against the click-bait line. "Is/as" did not stop it from sounding like the opening of an old claim that has started arguments. This really seems like a deliberate misdirection playing off an old argument to garner more attention for your post.