Dialogue trees are closest to what I'm considering, but I'm not sure I'll go with the traditional method used. Instead I've worked out a sort of 'binary' system for ease of response, yes or no, positive, negative or neutral, agree or disagree, etc. Responses for quick interaction while preserving immersion; rather than reading through an extensive amount of text to select something closest to what you want. Which also permits ease of calculating an NPC's admiration or aversion towards the player.
During investigating the internet for meanings about in-game dialog structures, I came to a similar conclusion regarding to phrases to be said by the player.
* They should not be (too) verbose, especially but not exclusively if voice acting is in play. This allows to pick a phrase but being still interested in reading / hearing the verbose one.
* They should be marked regarding to their effect on the interlocutor, so players not speaking the game's language natively need not understand the nuances in sentences.
* The choices should be limited to a few (perhaps at most 5 or so).
* The game settings may provide to switch on/off a kind of help for conversation in that choices are sorted regarding how good they fit the player character or the story.
However, such things are controversial anyway...