I'm curious why you think that is? Especially since you are likely to want to style the configuration for display to the user in many cases, having it be a document makes a lot of sense.

That is, if the value is something you would expect to be able to show to a user, then it probably shouldn't be at attribute. If it is a value that changes how you would show it, then attribute makes a lot more sense.

I also think a strong adherence to any preference between attribute and markup is a touch too dogmatic. The only real distinction at the language level is if you allow children, or not. If it can have children, it pretty much has to be a child and not an attribute.

Ok forget the difference between attribute and markup. What is the "right" way to think of this:

    <foo>
      <bar>1</bar>
      <bar>2</bar>
      <baz>3</baz>
      <baz>4</baz>
    </foo>

Why do you think there is a "right" way?