Try the following scenario:

• In MS Word, create a table with text in every cell
• In the RadRichTextBox, create a new document
• Activate Review/Track Changes
• Add some empty paragraphs or some text: change tracking markup will be displayed
• Just after the inserted text, copy and paste the table from MS Word: none of the cells has change tracking markup
• If you type inside the table, the new text has markup, but the text that was pasted with the table has no markup.
• If you use the right arrow on the keyboard to exit the change tracking tag, then if you paste the table, it seems to work correctly.

The default styles are not copied when using the CreateDocumentFromSelection method.

Workaround: Manually copy the styles:

var document = radRichTextBox.Document.Selection.CreateDocumentFromSelection();
document.StyleRepository.Clear();
foreach (var item in radRichTextBox.Document.StyleRepository)
{
    var style = new StyleDefinition(item);
    document.StyleRepository.Add(style);
}