Comment by vrighter

Yes it is, there's no rule saying you can't manually mess with the state transition function while designing and building the chain. It's still a fixed function at runtime. It's just that you don't need to do so in the first place, because this is done already after the markov chain has been evaluated, if temperature is set to nonzero (and some systems don't even really allow you to use zero temperature, they only allow you to make it really small)