Evidence with long length is weighted less since it contributes less to the energy.

When computing probabilities at finite temperature to finite precision, it should be possible to ignore long evidence (at least evidence which is long wrt the given sentence). If the shortest evidence for a sentence is very long, it means its probability is "marginal" in some sense (since the total energy depends weakly on the value of the probability field at this statement). For sentences which cannot be decomposed into simpler sentences using propositional calculus operations, "marginal" probably means close to 1/2.