I read in a walkthrough that if you tell Edwin that the Nether Scrolls are party treasure, his quest won't advance. Is this true?

If so, are there any mods to fix it?

I don't think that is a bug - I believe it was written that way intentionally.

Is it's an issue, just don't tell him it's party treasure. That way you'll still benefit from the Nether Scroll.

(about a week -game time- later...)

Edwin gained a whopping amount of XP, and told me he was starting to figure it out. I did say that the scroll should be party treasure, and Edwin's reply was something like "The scroll is mine, and any benefit to me will benefit the party" or something like that.

I'm almost sure what you say to him doesn't atter, he'll still benefit, and therefore benefit the party. His lore goes up 20 and saves go up as well :)

If you tell him it's party treausre, you shouldn't be having quest dialogues about it later. It definitely was written that way.

@Klorox, are you using any mods? I know there is at least one mod that changes this.

Just the Baldurdash Fixpack and Dungeon Be Gone.