Fair enough: I was reading the original comment as referring to (thermal) noise intrinsic to the amplifier design itself (as opposed to noise due to imperfectio

Fair enough: I was reading the original comment as referring to (thermal) noise intrinsic to the amplifier design itself (as opposed to noise due to imperfections in DC supply or due to coupling with some external transmitter), but this makes more sense, and we should consider the whole system anyway.