As a preface, I've played the game before... so I almost didn't catch this. Please fix it before too many new players encounter it by mistake!
Here I am in chapter 3, and Hexxat initiates a dialogue, beginning with, "You hardly seem the cosmopolitan type, Charname, and you're obviously not a local. What brings you to Athkatla?" The typical responses are there ("Blah blah Irenicus," "Blah blah Imoen," and "Blah blah shut your face") ONE of the options spoils the much-later-revealed twist
having to do with Imoen and the PC.
I'm preeeeetty sure you're not supposed to know that before you meet up with her again. I haven't played in ages, though, so I could be wrong. It's an easy and super-forgivable oversight, especially for devs who've known the twist for several years (you guys are awesome!), but please fix it as soon as you can. Maybe do a quick run-through of the other new dialogue to make sure it's not spoiled anywhere else??