The most concise and precise way to write a language is generally in the language itself too.

Doesn't really apply to HTML.

Using indentation instead of XML-like opening and closing tags is way more concise, and encodes exactly the same information.

It's shorter, I don't know about concise though I suppose that's a subjective point anyways. While it's generally exactly the same there are some corner cases involving formatting rather than structure tags where it's not always 1:1.