This information was posted recently on the IBM public technote web site, but I thought it would be good for all my readers. It fell (for me at least) into the "learn something new every day" category.

This information applies if you are using the "Remove documents not modified in the last xx days" setting. Go to File | Replication | Settings, then choose the "Space Savers" tab. An image can be seen in figure 1. That setting purges documents from the current replica if they haven't been modified in a certain number of days. "Purges" is the key here - there is no deletion stub created. So it would be possible for documents purged through this method to reappear through replication.

I haven't tested this, but if they reappeared, it could be the case where the server again recognizes them as not modified and purges them again. If someone has been able to test this, please post your findings as a comment.

More information can be found at the original technote.