I like suggestions already made regarding including portraits in the dialogue interface of the NPCs you are talking to, and making the descriptive text better defined.
I think it would also be a nice option to have different themes to choose from of the UI, so for example, you could pick the wood theme like it is now, or an ancient leather book style theme, or a classic stone theme, or a modern theme (which would be more vibrant, and perhaps look more sleek and less old fashioned)
And about exiting dialogues, maybe instead of making up ways to say 'goodbye', or just saying 'goodbye' (which seems a bit clunky), there could always be an option for [End conversation] available (with the words included in brackets as I showed).