Enviado desde mi iPhone con Tapatalk
It goes like this:
S-on + SuperCID + jb RUU = brick
S-off + SuperCID + jb RUU = no brick
Basically you're fine because you're s-off. The RUU returns your phone to a stock state which includes ROM, recovery, and firmware. Your unlocked bootloader and s-off status will survive the process though. All you need to do afterwards is flash TWRP again, flash the 2.15 firmware, and you'll be good to go.
Sent from my Evita