Reading a biography of Nietzsche, and it got me thinking. We don't really know what caused Nietzsche's madness in 1889, but syphilis and brain cancer are both candidates. Let's assume it's one or the other, and that Nietzsche doesn't contract it, and remains sane. What would the consequences be? Does he still reach the fame he did IOTL without the tragic-romantic end to his story? If he does, and he doesn't have his sister "reinterpreting" his philosophy for him, how does that change the reception of his ideas?
I don't think Nietzsche's death is really seen as a significant contribution to his fame, though the image of him glaring into space and babbling away on his deathbed does fit the general persona that's been handed down.
As for his sister re-interpreting things, how important was that in the Nazi's embrace of Nietzsche, and the subsequent post-war stigma attached to him(eg. the movie Rope)? Nietzsche's style was so blatantly outrageous, that unless in later life he had written an official explanation saying "Okay, just to be clear, all that stuff about killing the weak is really just a metaphor for my objections to the condescending nature of Christian morality", and attached that to all copies of his other books, I think he's pretty much bound to be misunderstood by anyone looking for poetic rationalizations for cruelty.
Not that I think for a second that N. is responsible for the Nazis, just that, it probably didn't require his sister's intervention to get Hitler to think he was on their side.
Unless it's the case that, without her lobbying, Hitler never would have gotten into Nietzsche. I think I read somewhere, though, that it was actually Mussolini who was more interested in Nietzsche, and tried to engage Hitler in discussions about him, but found Hiter's understanding superficial.