The content area of RadEditor is a standard iframe element and if these entities are rendered properly in an HTML / ASPX page then they will be rendered as expected in RadEditor too.
I tried to render the provided entities in a standard aspx page and noticed that they are rendered as empty square boxes in IE and as in Firefox. You can see my test in the following video: http://screencast.com/t/0AAx4Y6M7k
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