Just moving from Word 6 to Word 97 and back again can cause interesting problems, even if you have the latest filters. Sometimes file conversion is the best solution. If the purpose is to get a document from one format to another, and it's going to stay in the second format, then file conversion is quite appropriate. The author can also view your comments and make the associated changes. After revisions are accepted or rejected, they no longer appear as revisions.
Comments can be tricky, because they are automatically removed from the file.
If they are hidden, people can view and print the file without knowing the comments are there, but anyone can make them visible. Since comments often include discussion among the writers, reviewers and editor, you may want to ensure that whoever does the final pass on the file removes all the comments before the document is made public. Archive a version with comments if you need them as an audit trail. I had to design a template for something else recently. I didn't do a full blown template with toolbar.