Comment references - comments without start and end, just a position in the document, are not imported from docx and RTF document.
RTF: such comments don't have their annotation start ('\atrfstart') and end  ('\atrfend'), and only have '\atnid' tag. In the specification such comments are referred as 'annotation is associated without an annotation bookmark".
Docx: such comments are denoted with 'commentReference' element.

Steps to reproduce:
1. In MS Word, add comment without having a selection in the document.
2. Export the document to RTF or docx.
3. Open the exported document in RadRichTextBox.
Expected: The comment is imported.
Actual: The content is not imported.