Does the conversation make much difference? Other than the npcs response, does their action change much? When talking to a daedra, you can answer as their servant (your will my lord) or like an a hole (I'm not your patsy, just give me the artefact) and they still give you the quest. At least in oblivion you could a hole certain characters into fighting you.

I remember a particular Markarth city quest that gave you a lot of choice in terms of conversation options. Something about unravelling a Forsorn conspiracy.

For the most part your conversation options make very little difference.

but did it alter the quest - could you fail the quest or change it for having said one thing or another?

99% of the time, no difference.

Once the quest is "done" and you go to collect your reward, nothing changes. There really are no dialogue choices then. Just a thanks and here is your reward.

At the very least they could alter the reward - have a "happy quest giver" reward and a "grudging quest giver reward"

--> "Here human, you're an a hole but take the mug of Molag Bal. Now piss off."