Before revision:  We denote our paraphraser "unbiased" because the mode of our model 's output probability is centered around a copy of the input sequence, which in our case represent the best case scenario where the MT system output matches a human reference.
After revision:  We denote our paraphraser "unbiased" because the mode of our model 's output mode being centered around a copy of the input sequence, which in our case represent the best case scenario where the MT system output matches a human reference.