On topic of Luther nails it. I have no horse in this race whatsoever, so what interests me about the discussion is how we as individuals (and as groups) deal with information as it is handed down to us. For some, the reasoning is if it was reasonable to have happened why not believe it happened? For others it is more if there is no direct evidence it happened, it likely did not. To me both are flawed arguments. Why? Because the one simple reality is we cannot know. To make any other statement is reading into the story more, or less, than there is. (I have to include myself here, as I have fallen into this error more than once!).
And does it really matter whether Luther posted this on church doors or not? Seems Thomas has the right approach. What was the result of that document, both what might have been intended and what it turned in to. Surely the progress of history is what is important here. Dealing with minutia less and dealing with the big picture more seems the right way to go.