He doesn't, though. ._. Naval Santiago doesn't have an accent or anything and I am fine with him using a manly man voice, but he has a definitive way of using irony in my theater-of-the-mind. He doesn't use it spitefully or in lamentation (which is some of the most whiny, cringy type of sarcasm a medium can offer), but rather to make serious situations just a bit more light-hearted when the going gets tough. "It's almost like we're fighting for our lives or something", as an example, is a tricky line of sarcasm for a voice actor to say without ascribing an emotion to it. It can sound very different in different contexts. For example, in an angered, raised voice, it sounds like a scold or a threat. In a cold voice, it sounds annoyed and professional. In a more jovial voice, it's more like poking fun at the situation.
And the thing is, I know the way I would say it. And the game doesn't have to know how I think the lines are said, in order for my interpretations of those lines of sarcasm to remain valid. If I thought it jovially and the NPC reacts violently, I can build on that reaction as the NPC feeling disrespected by me trying to make light of the situation. If I thought it angrily and the NPC reacts jovially, I can build on that reaction as the NPC being slightly intimidated and trying to use a nervous laugh to stave off my rage. If I thought it coldly and the NPC reacts indifferent, I can build on that reaction as the NPC being in-line with my own.
It really doesn't matter what emotion I ascribe to the line (well, within reasonable limits), almost always an NPC's reaction to a selection of text can be rationalized in some way. That is called theatre-of-the-mind and it's a powerful tool in maintaining the suspension of disbelief, more so than, say, clipping issues.
That is a very good perspective, actually. I hadn't quite realized the way Skyrim did things, but in retrospect, it really did bother me. May I ask if you have played New Vegas? If so, what are your thoughts on the dialogue options in that game, compared to Skyrim's? To me, it would seem as though the lines in New Vegas are more to-the-point than Skyrim's. I might be wrong though (note, English is not my native language, so I might be used to just brushing it off as a culture thing).