But Turing completeness is also too broad. Otherwise Power point animations and Conways game of life are programming languages.

Yes. So a criteria that is below Turing Completeness but which wouldn't make markdown a programming language. Shouldn't be _that_ hard to find such criteria. E.g. "Has some form of logic/flow control". Can perform computation/"execute". etc.

I mean, CS is famously bad at exact definitions [1]. Why should we have one for what a PL is? Just do what humans have been doing for millenia, how is it commonly used. A tomato is a vegetable from a culinary perspective, and HTML is not a PL based on its use case and its literal name.

[1] what is a low or high level language? Strongly typed language?

I will take this over HTML