The bar for me is whether the language describes an executable program that has state and control flow.

You could perhaps be generous and describe the DOM as a (write-only) state and the parser as a control flow. I don't, personally.

HTML is just a data container format to me. Belongs with the likes of XML, JSON, JPG, PNG, GIF, MP3, MOV, etc.

The umbrella term I'd use for all of these is "coding". That's the skill of understanding structured languages and format specifications, and understanding how you can and can't piece things together to make something coherent. This is a critical requisite skill to programming. But programming is more.

Programming is the art of juggling of state and control flow in clever ways to trick funny rocks into computing something you don't know. It doesn't need to be general purpose, but I would argue it indeed needs to have a purpose. It has to be something more than just a pile of declarations you know from the outset. Otherwise it's just structured data.

Not really. If so, you might as well consider the stuff you can use to format a comment here on lemmy, as "programming". That's conceptually more similar to HTML as what programming actually is.

quote

some title

Ooo hyperlink

Etc.

You port Doom to it.

@jackpot @KittyCat implementing a brainfuck interpreter for it is a useful method

By building a simulated Turing machine, usually... or at least by demonstrating that all the components to do so are available.

A PowerPoint, word document or even a text file or picture. There is only a description in the file of what it holds and it's up to the program that reads it, how it will visualize or interpret it.

A word document or PDF would be the closest.

Markup language vs programming language is similar to the difference between a font and a typeface. Sure, they're different but to the layperson, they might as well be the same thing.