Haven't any of you gained a level after a dialog? Minor spoiler - like the fisherman tricked into digging out the Mind Flayer. Obviously, you get XP (and some weirdly underpowered gear) if you kill them, but you also get XP if you send them away without killing them. I have not paid attention to the amount, but you can get from level 1 to level 3 just doing a lot of exploring and dialogs with very little fighting. So this thread seems weird like I could see discussing the amount of XP, but it seems to imply there isn't any which is untrue.
Decided to test this, and I was totally wrong. What I was seeing was XP given for starting/advancing a quest. So like when you come across Lae'zel and talk the Tieflings into walking away instead of killing them, you get XP for Advancing the Lae'zel quest. You get nothing for avoiding fighting them. Avoid the fishermen and temple raiders...same no XP for avoiding the fight. So...yeah I agree that there should be.