It's a real shame HTML5 ever became a thing. We would have been a hell of a lot better off with a simpler spec - perhaps not xhtml as is, but certainly one that keeps the simplicity of well-formedness around.

Such a mess nowadays - and it's not just `<p>`, similar special snowflake rules exist for `<a>` and `<button>` too, and indeed lots of elements have special quirks that make composability a pain.