I am having the same issue with a file that I am working in. The problem I have is that when I pull the markups into Revit(v.2013) I view them and make my comments within Revit. I then repost the the DWF. When i go to open in Design Review every sheet that contained an existing markup will post that error. I understand how to get rid of the error message but I would like to retain the markup so we can retain that information for ongoing purposes. Maybe this is a Revit issue but is there a way to achieve this?