There are several ways you can export comments:
- export the module or artefacts containing comments as a Word report using the built in report formats. There's a check box that let's you export comments
- export the review which will include the review comments
When importing a Word document you can import any comments in that document as comments in the DNG module, but there's no way to import comment replies back into DNG from external sources.
What my customers normally do is have all parties work in the same DNG instance and then they just add comments directly. The other option, which isn't as good, is to have a custom attribute on your artefacts for comments. The problem with this is that they are easily changed and overwritten.
Comments
You might want to look at REQIF.