The mass merge comes up with a pop up where there are conflicting declarations on the records that are being merged.  This message comes up at the point of merging, it tells you the conflicting declarations cannot be merged and tells you the name of the record.  You then have to make a note of the name/s during the merge, find the records and merge them manually.  Otherwise, if you go to the global delete stage, you will lose the information.  On similar scenarios (eg where there is a scanned declaration), the records are not merged and are exceptions in the process.  I believe it's more efficient and less open to error, if these conflicting declarations could be exceptions as well.  it would keep the process slightly more steamlined to have all exceptions together (rather than have to have a separate process for the conflicting declaration issue)