> I think the part where they're trying to abstract out a `content` method could be made to work by adding braces, so that the `&self` borrow goes away earlier than the end of the function.

Not in that case. It helps when dropping a borrow earlier avoids to violate the borrowing rules, like in this case:

    let mut a = [0; 20];
    {
        let b = &mut a[2..4];
    }
    let c = &mut a[6..8];

In the example from the blog post, content borrows the whole struct, and you can't drop the borrow earlier since it is used in the next line.