Restraint wrote...
They don't want to show the full line because it undermines the presentation, takes up a lot of UI space, and in any case wouldn't be a perfect solution to the problem of unexpected outcomes.
Origins for example was designed with full line dialogue and silent pc in mind and still there was more than one situation where the intended meaning of the sentence I chose did not mesh with the reaction it got. The problem would be exacerbated with a voiced PC who communicates like a real person.
I don't see how it wouldn't be a perfect solution. In origins, you weren't shown the tone -- but I maintain that the tone can never be changed, despite what some people may think.
In DAII, however, you have the tone.

*reposting this to further my point*
Take for example the highlighted option:
Then we fight.
It's aggressive and to the point. That's good. We know the tone of what's being said.
The actual response is
We'll take the bastards down with us.So, what is often proposed is that when the option is highlighted, after a few seconds the actual response is shown at the very top of the screen. Or the bottom. Either as a surtitle or a subtitle. It doesn't matter.
Then, players that want to know what they're saying know both the tone and the actual response.
So I think that solves the issue of unexpected outcomes.
Undermining presentation? I think that's relatively minor compared to undermining peoples' control of the PC. I think that can be solved by re-reading the paraphrase before selecting, where that would be what's fresh in the player's mind and wouldn't present an issue of "I just heard what I read!"
But that might not work, and it's not something I'd need to do. Admittedly, I wouldn't be bothered by reading the full line and hearing it, mainly because I read to myself instead of aloud.
Now, this isn't to say presentation isn't important. But I think player control should be prioritized over presentation.
I would know what's being said, along with how it's being said, and not feel like my PC is not my own.
But this part of your post isn't something I'm truly fit to argue so I shan't continue, for fear of saying things that are either irrelevant, strawmen, or just idiotic and absurd.
As for the UI, well, I don't know what's meant by "it takes up a lot of UI space".