We used to have an issue with Adobe 9, in that periodically, a reviewers xml files got overwritten and comments were lost.
We found out there was an issue with Adobe 9.2 and that a fix was done on 9.3 (2465483: Fixed a 9.2 issue where a reviewer’s xml gets overwritten and comments are lost after a user exits and opens the PDF again in shared review, the previous comments were deleted).
We therefore downloaded Adobe X for all our users, however, this issue is still ongoing. What happens is that a user may publish, say 200 comments to a PDF and then close down. When they open up the next day, they get message saying the 200 comments have been published, click here to accept. When they accept, the comments are deleted.