Buying a used FRS/BRZ is risky in my opinion, more so if it is a used manual transmission.
The car is sort of marketed as a revving machine. So I would only assume that some drivers are less experienced and will thrash the car, especially engine and clutch. How many, not sure but it has to be a lot right. Meanwhile the experienced conditioned manual driver would know how to treat this type of car.
I would be leery of a used 86. My first thought would be, what was their break in period like?