From this point on, a major aspect of G-d's work is through covenants, first with Abraham and then with Israel. It is highly questionable if this laudatory lesson can indeed be derived from these texts. In the case of Moshe's prayer, he is pleading with G-d to be merciful, to conduct above and beyond the dictates of justice and reconsider his decision. It seems to me that G-d's commitment not to bring another Flood to destroy the world does in fact indicate regret. This commitment is given unilaterally.
Murder is the most severe crime that one person can commit against another.
But there is no general command concerning justice. Nor is Noah's dedication to insure justice mentioned in the text. In the case of Noah, there is no mention of sedakah or of justice, only of murder, the most serious of all crimes. Why no other issues of justice are mentioned is something that calls for an explanation, which I do not have at this moment. Neither appears in the text, nor is there a hint that the Divine promise not to bring a Flood depends on anything.