Perhaps you can explain where your reasoning differs from mine using the vaccination/autism example?

I don't have sufficient knowledge of medicine to have a discussion about vaccination and autism. Either way, it's also an irrelevant discussion.

Absence of evidence is not evidence of absence

Of course it is. But it has be weighed accordingly.

but absence of evidence after a search that should have found evidence if there was any evidence to be found is evidence of absence.

You've not given me any reason that it "should have found evidence". I've asked you how much documentary evidence the average itinerant preacher left behind. Even ones that were relatively well-known at their time. How can you say that Jesus should have left documentary evidence, when you don't know if other itinerant preachers left "documentary evidence"?

I don't have a default position that there is nobody on the footpath outside my house.

I have. It's the default position because most moments there's nobody on the footpath outside my house. The prior for it is higher therefore.

What was the more common occurrence though in the 1st century AD: real itinerant preachers, or stories about fictional itinerant preachers who were nonetheless believed to be real? Where are the evidence that such fictional stories existed?

Answer: the former. Thus the default hypothesis should be that Jesus was a real itinerant preacher -- because the prior for that is significantly higher.

Regarding your other arguments, I do not find the argument that the Jesus story is exceptional because it has elements X, Y, Z etc. not found in other messianic stories persuasive because it is a highly general argument. You can always find something in your favourite story which is not in other commonly-known stories and claim that this is evidence your story is exceptional.

You're disregarding everything I say. I'm not saying anything is exceptional in the Jesus story. It's not any more exceptional than the Mohammed story, or the Joseph Smith story. It seems to me a very ordinary story if it's based on an actual human being, an actual preacher/faith healer/etc.

It'd be an extraordinary story if it was completely fictional, because other than some specific fictional elements ( the humble, danger-filled but also miracle-filled birth -- following the mold of Moses/Perseus, etc -- the deification/glorification after death ) it doesn't follow the mold of such stories at all.

The fact that some elements of the story are relatively constant is not persuasive evidence of a unitary historical founder either, any more than the fact that the basic story of King Arthur or Batman stays the same despite many reinterpretations is evidence that there must have been a real person behind those myths.

Actually the story of Arthur has significantly changed, between the original welsh tradition and the time he was enhanced to King of the Bretons by Geoffrey of Monmouth.

But more importantly, in those stories the most crucial elements remain the same. Batman fights against criminals dressed as a giant bat, motivated by the death of his parents. Robin Hood leads a band of merry men, steals from the rich, and sometimes gives to the poor. Hercules was a monster-slaying son of Zeus with enormous strength. The core of the story is summarized in the relevant elements.

Also the prior of successful costumed superheroes being fictional is much higher than them being real.

In the Jesus story the most non-meaningful elements remain the same, but the ones that would be most widely known: e.g. he was of Nazareth. The public crucifixion. There's no inherent meaning or moral in that -- not nearly as obvious a meaning as "The Heavens themselves proclaimed the significance of his birth by having a new star appear in the heavens above him" -- whose analogies we see in the semi-deification of the Kims in North Korea. But because the crucifixion was a public event, it had to be present in every story and be given meaning it did not inherently possess.