I think this is a relatively important thread for this forum and no one really ever engaged with Johannus.
My take on the unreveal is this, and if you're paying attention it will more-or-less look like the one that I have posted here in other threads.
Anakin is very Lancelot-ish. It's not that he appears to be a little shady or a little less dedicated than Obi-Wan... he's almost too dedicated. He's the shining star and the unfallible one. He's the greatest among them... Until he falls to the Dark Side.
But this post is more about the reveal.
Again, I've said most of this before... but here it is again. There is another Vader. As Johannus said, not Vader exactly as we know him, but a close prototype. Anakin fights him (for reasons I won't go into here, but they're not that good- it's clear that Dark Anakin wants to kill him), damages him, but Obi-Wan stops him from killing him. They argue, Anakin's view being distorted by his turn to the Dark Side. This is when Obi-Wan realizes the depths to which he's fallen. He tries to talk Anakin down. The argument leads to a fight. This fight then leads to a duel to the death. The fight brings Obi-Wan to the brink and he taps into the Dark Side which gives him a slight upper hand (the theoretical high ground) and he delivers a fatal blow to Anakin- knocking him off a catwalk above a molten pit. Obi-Wan realizes what he's done- what he's momentarily become- and reaches for his friend. (Or does he?) Perhaps Obi-Wan says that together they can bring him back from the Dark Side. Perhaps Anakin realizes that he will never be free from it. Perhaps he let's go. Instead maybe Anakin doesn't trust Obi-Wan as he comes toward him. Maybe also, Obi-Wan, crushed with grief, decides to put his friend out of his misery and cut the railing supporting him. Maybe he simply does nothing. I'm not sure yet.
But the important bits- Darth Vader gets away. Anakin dies. Obi-Wan is responsible for his death. Obi-Wan, returns to his friends- to Mrs. Skywalker. To preserve the memory of his friend (and just maybe to ignore his own guilt in the matter) he begins the lie- Darth Vader murdered the Jedi hero Anakin Skywalker. Anakin's lightsabre is placed somewhere for heroes.
The tragedy is complete. The end.