It seems improbable that someone would be able to fake his own death so many times and so effectively, but it genuinely seems to be the same guy over and over. A bunch of people over on /r/conspiracy keep attributing it to the Tleilaxu, but everyone knows you couldn't make a ghoula that good.
The Duncan Idaho is a folktale's character of the last Fremen, it was developed using early Fremen figures from Zensunni mythology. He's the Ultimate Hero of Fremen mythology, a kind of messianic figure. So the numerous sightings of Duncan Idaho can be compared to the apparitions of the Virgin Mary on the Earth of origins.
With the finding of Leto II's diaries in the previously unknown no-chamber on Arrakis, even mainstream bene gesserit historians have acknowledged the fact that the Tleilaxu did make him over and over again for Leto II.
I'm Duncan Idaho!
A bunch of people over on /r/conspiracy keep attributing it to the Tleilaxu, but everyone knows you couldn't make a ghoula that good.
You underestimate the Tleilaxu. Why do you think they've survived the proscriptions of the Butlerian Jihad?