"But is there anything to be gained by dwelling on the unfairness? Does it make either of them feel better?"

That's just mostly my reasoning for what I find upsetting, not necessarily theirs. :)

"And I guess the point of contention in this scene is that Shen Wei is insisting is is fair and right. That ZYL is worth it, and it's a completely reasonable repayment of a debt."

I do agree that once they're in this situation, this is pretty fair and right. :) The unfair part (to me) is being in this situation.

"And then I think of ZYL's loving smile in YOHE when he says, "You've already repaid it" and I wonder what he's thinking about it then."

♡♡♡ And it's "many times over", so it's not just about this, it's about everything.

"I think narratively, there had to be a cost. (That's something the drama "fixed" from the novel.)"

Oooh, on one hand, ZYL's blindness in the novel is just fixed, on the other hand the novel is the one with the extremely clear rule that the Dial takes a part of your lifespan. So putting these two things together is again the writers creating their own neat and intricate puzzle, isn't it. :D