Create different options for pasting (keep formatting, merge formatting, use destination styles). At this point, the document default styles are not copied in the document fragment, thus their loss is observed. 

Loss of formatting is also observed when:
- copying from RadRichTextBox and pasting in Word
- copying from RadRichTextBox and pasting in RadRichTextBox in another process.
- copying from Word and pasting in RadRichTextBox