I also know that Germany has proscecuted several people of the years for holocaust denial regarding their specific claims about the Diary. To do so, the proscecutors had to demonstrate two things:
A. Neither Levin nor Otto Frank wrote the diary (as claimed by some)
B. The published book version of the diary is not a heavily edited / modified and unrecognizable version of the original (as claimed by others)
As a result, the original diary was forensically, historically and linguistically examined. The German investigation determined that the published version very largely reflects the original diary and that the diary was written by Anne Frank. The report also acknowledged that there have been instances of notations added in ball point, as well as indications of minor editing or modifications. Otto Frank never claimed that the published version was a verbatim copy.