The nature of inter-relational appraisal is such that you are seizing upon some limited aspect of someone's personality, an aspect that only appears at certain times and in certain conditions. Further the act of naming implies a relation too. That person is a certain way in relation to how you yourself feel about the person.
Of course there are certain aspects of a person that can be broad enough that they do a good job of predicting someone's behavior, or predicting a certain set of outcomes if one is to interact with a certain person.
But an appraisal is also necessarily imprinted with an affect, like "good" or "bad." And affects one casts at someone usually evoke similar affects in the other, and the two reinforce each other.
And sometimes a jerk is as a jerk does.
