Having analyzed the scores of the model scanning from both directions, we found that the original scores (from left-to-right scan) at the stages "者" and "宿" indeed get better if the model scans from right-to-left.
the score at the stage "露" deteriorates because the useful feature "者" (a past non-adjacent character for "露" when scans form right-toleft) still cannot be utilized when the past context "宿者" as a whole is unseen, when the related probabilities are estimated via modified Kneser-Ney smoothing (Chen and Goodman, 1998) technique.