but I'm not so sure.
Obviously Rayleigh uses Haki, but that doesn't necessarily mean that's how he blocked Kizaru or cut him; it could just be that Rayleigh's yet-undisclosed abilities counter Kizaru's.
He's called the DARK King for one thing. One assumes that this means he was the man in the Pirate King's shadow, but it might have a deeper definition. At the very least it's worth consideration when he's fighting a Light man.
His name is Silvers; again we assume that this is just to fit with Gol D Roger, but who knows. It's worth noting that silver is a material used to make mirrors, and that Rayleigh's sword could very well be made of silver and be a natural counter to Light logia. (like moisture is for Croc)
Most convincingly:
I don't know if this has been seen around here, but I saw this on another board and thought it was pretty interesting.