RadEditor is a text editor based on HTML, thus, you need proper HTML in order for the text to be rendered properly. When it is encoded, it is transformed to plain text, and it is no more markup that can be rendered by the browser. RadEditor has no capabilities to programmatically capture and decode encoded HTML, moreover such behavior would be inappropriate.
In order to properly add content to the editor, you should make sure it is proper HTML, therefore, when programmatically adding encoded HTML, you should first decode it.
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