I like this question as well, and I agree with everyone's opinion.
Although, I believe that O'Brien wasn't necessarily feeling a sickness
towards death but towards the fact that the men were greeting the man
as if he were still alive. "The plant specialized in pork products...
[my job was] removing blood clots from dead pigs, declotter," this
shows that he has been around death, even though it's animal death,
for a good amount of time (O'Brien 42). When O'Brien feels the "moist
sickness rise up in [his] throat," it was after he saw the soldiers
converse with the dead man (226). I believe that he was comfortable
with death but since he was new, seeing the soldiers interact with the
dead man made things different. I don't believe that all the soldiers
are comfortable with death, i just think that they developed the mind
that the war involved death. I believe, that they believed that in
order to go home they would have to kill and be okay with it. Ted
Lavender was only comfortable with death because he "popp[ed] four or
five tranqulizers every morning...[it was] his way of dealing with the
realities" (230).