If we are in a simulation, would it be immoral to try to find out, because that might jinx the purity of the simulation creator's results, thwarting his intentions?

It might jinx the purity of them, but it might not, maybe the simulator is running simulations of how fast we determine we are in a simulation. We don't know, because the simulator isn't communicating with us in that case, unlike in Albert's case where Albert and his programmers are openly cooperating.