What is the first description we hear of Kurtz? For what activity is he praised? How does the praise bring up the novel's frequent oppositions between light and darkness?

1) As to me, I seemed to see Kurtz for the first time. It was

a distinct glimpse: the dugout, four paddling savages, and the lone white man turning his back suddenly on the headquarters, on relief, on thoughts of home -- perhaps; setting his face towards the depths of the wilderness, towards his empty and desolate station. I did not know the motive. Perhaps he was just simply a fine fellow who stuck to his work for its own sake. His name, you understand, had not been pronounced once. He was `that man.' The half caste, who, as far as I could see, had conducted a difficult trip with great prudence and pluck, was invariably alluded to as `that scoundrel.'

2) Gathering ivory; `Ivory,' jerked the nephew; `lots of it -- prime sort -- lots -- most annoying, from him.'

What is he being praised for?