When the system does not provide enough information to preserve justice, it's up to other individuals to ensure fair treatment. Few will admit this as a motive even to themselves when it would be more personally rewarding to let mistakes or ignorance slip by, but it is the basis of many actions.
edit: was trying to preserve an original thought, not restate something else encountered before ._. The loss of information obtained from the current situation (unable to be communicated within the current system in a useful way), and the effect of this potential information loss on decision making due to the uncertainty of future benefit and cost of remembering are the salient points of the thought. This is related to the manipulation of values, and priorities of action, when the source of those values is not known or understood.
Note that it isn't mentioned whose mistakes or ignorance, the definition of rewarding or whether that reward assumes a constancy in factors that might have other influences.