1) MY98 WRX, ~125,000kms
2) Brass button clutch
3) Nope
4) Snapped the output shaft between 2nd and 3rd
5) Shaft replaced with a PPG item, around $2800 including labour
6) Fuchs GearSyn or something like that

I think my situation occured because the box was upgraded with PPG 1-2 straight cut synchro gears. Given they are ridiculously strong, the force just shifted to the next weakest point, the shaft. That being said, RMS said they have never seen it happen before.