Thank you for everyone that answered. A couple of comments, and the final answer to my question:
As several posters have mentioned, Otto Frank, before the original publication of his daughter’s diaries, removed several passages concerning her sexuality and several personal comments Anne Frank had made about the other occupants of their hiding place. (Which he was perfectly justified in doing, in my opinion.) Afterwards, other people reading the diaries thought that the whole text should be published, and the whole text is now available. I think the Comprehensive Critical edition of her diary is the most complete (but I would check on that before ordering it, if what you want is the most complete text of her writings.)
What I was wondering is about an article in “Der Spiegel” magazine saying that the diaries were a hoax. I’m not surprised to find out that some lunatics have claimed the diaries were fake, but a major german magazine like “Der Spiegel” claiming it would be surprising.
An internet search revealed the answer! Go to this link:
Anne Frank House
Click on “Diary”, then on “Diary Current”, then on “Authenticity Diary”.
Here’s what they have to say (in brief):
Several (german) people had attacked the authenticity of the diary. Otto Frank filed several lawsuits against these people. In one lawsuit, a court in Lübeck (Germany) ruled, in 1960, that the diaries were authentic, after research into the authenticity of Anne Frank’s writing.
Another ruling in 1978 prohibited another person from writing articles claiming the diary was fake.
Two cases in 1979 were dismissed because of freedom of speech issues, but the court ruled that if an injured party filed suit, slander changes could be pressed.
Finally (and here’s the answer to my question), the most involved case:
In 1976 E. Römer published pamphlets claiming the diary was a forgery. In 1977 the district court in Hamburg fined him, but during the appeal stage another right-winger, E. Geiss, was condemned for distributing in the courtoom other pamphlets saying the diary was fake. An appeal was filed and the Römer/Geiss cases were combined. The German Criminal Court Laboratory (Bundeskriminalamt or BKA) was asked to examine the diary. Their conclusions: paer and ink had been in use dsometime during the war, but they also said later corrections to the pages were made with a ballpoint pen (and ballpoint pens were unavailable in World War II). In 1980, “Der Spiegel” (here we go!) published an article about those findings, which claimed “this undermines the authenticity of the document even further”. Otto Frank died in Augutst 1980. The manuscripts were left to the Dutch State, who deposited the documents with the Netherlands Institute for War Documentation (Nederlands Instituut voor Oorlogsdocumentatie or NIOD). Otto Frank’s heir was the Anne Frank Fund in Basel, which also inherited the copyright of the book. The NIOD published the complete diaries of Anne Frank in an annotated version. The State Forensic Science Laboratory (Gerechtelijk Laboratorium) in Rijswijk was asked to examine the diary. The Gerechtelijk Laboratorium asked the BKA to indicate where they had seen ballpoint ink. The BKA was unable to point out a single alleged correction in ballpoint ink (surprise, surprise!) After all these years, the case was resumed in 1990, Geiss was sentenced to a fine (Römer had since died), but the fine was set aside on appeal because of the statute of limitations on the offence.
Conclusion:
So I guess “Der Spiegel” did, in fact, in 1980, publish an article questioning the authenticity of the diaries, following a conclusion by a german scientific laboratory. But since the german laboratory was unable to justify its findings during a second examination by another laboratory, I think “Der Spiegel” should publish a retraction and apology.
Whew! That was long.