Final answer:
Melville portrayed Nippers as afflicted by ambition and indigestion, resulting in irritability and restlessness, but acknowledged him as a valuable and presentable employee.
Step-by-step explanation:
Melville deemed Nippers as the victim of two predominant evil powers: ambition and indigestion. Nippers is described as a young man with an irritable disposition and a restless ambition that is unsuited for the menial duties of a copyist.
His ambition manifests through a desire to engage in professional affairs beyond his position and through interactions with questionable individuals he refers to as his clients.
His indigestion is illustrated by his nervous testiness, irritability, and the continual discontent with his work environment, particular the height of his table which he can never adjust to his satisfaction. Despite these shortcomings, Nippers is acknowledged as a valuable employee who writes neatly, demonstrates a gentlemanly demeanor and presents himself well in attire.