OKay. So. Thoughts. Please excuse meandering. It's 7am and my brain is not yet fully operational.
Point the oneth:
S1 has set up precedents of wounds getting infected, causing delirium and resulting in amputation (whether by colleagues or self-inflicted) in episode 6. It has also set in place characters in fevered deliriums seeing flashes of people/places that upset them - Stede seeing Mary with the letter, his father laughing at him with the murdergoose and a hostile Alma in episode 4.
Point the twoth:
Last we saw Izzy, he had his foot mutilated. This is not a man who would ask for help when injured, so I bet he doesn't do anything about the infection until it's too late because….
Point the threeth:
By the time we see Stede's training montage with him, Izzy has a wooden leg. In the scene with him and Stede fighting on the beach, he has both feet.
Point the fourth: Bearded Stede is an idealised pirate: he's dressed like a showy pirate would be. He has leather trousers. He has a beard. He's masculine and holding his own in the fight on the beach.
Point the fiveth:
Bearded Stede has Izzy's sword.
Point the sixth:
We've seen that framing and expression before on Stede's face on only one single occasion.
So my theory, as loosely mentioned yesterday, is now elaborated upon.
I'm now absolutely convinced that the bearded Stede, the dashing romantic hero-looking bugger, is all Izzy's heightened fever dream while he's delirious and infected.
He's reliving the moment that turned his life upside down: the day he ran into the man who "bested him at swordplay" and who his boss found "fascinating". He's disarmed, his sword is in the hands of the man who turned his life upside down when he "done something to my boss's brain".
And ngl, I am giddy with excitement that if this is Izzy's fever-dream, he's the one butching Stede up. Like sir, contain your fever-addled ravings! Some might even call them thirsty. If his fever dream involves Stede slashing his shirt to ribbons I will punch the air in glee.
And then, he goes to train said fellow and feels the need to slap him on the arse during said training.