Allow the html formatting provider to allow exporting the italic/bold/underlined text by using the corresponding html tags instead of text-decoration css styles.

Resolution: 
This issue is addressed in the new version of the control - RadRichTextEditor. Please use the new control instead the RadRichTextBox. 

You can use the following code snippet:

HtmlFormatProvider provider = new HtmlFormatProvider();
provider.ExportSettings.ExportFontStylesAsTags = true;