So, even though the remove() method doesn't work on the above part of my header I was able to get the desired behavior working with a mix of Mithril, css, and plain-old javascript. Because all the nodes inside of the html scaffolding above were added via Mithril they needed to be removed via Mithril with m.mount(element, null). But because the html scaffolding itself works outside of the single page app, I used javascript – classList.add – to add a css class to those items set to display:none. A little convoluted but it works.
