the chest riddle answers are all information available from speaking to characters in the game - those nonessential comments that are usually just for window dressing. The idea that it didn't just rely on educated guesswork or obscure general knowledge made you actually read and remember those comments rather than ignoring them.Certainly "palimpsest" is obscure enough that most people would need the clue in the game rather than just knowing it. But it's not strictly correct that you can't find the answer until after you need it:
* It's mentioned in one of the houses in the Karthal slums (library? the one with the scholar hireling I think)
* You need to enter Karthal first time through the sewers
* You *can* do this before you've killed Montbard in the Lost City, but Zouleika isn't at the entrance to meet you until you do. So the quest timeline makes more sense to kill Montbard, report to Jon Morgan, get the quest to enter Karthal & find Zouleika, then enter Karthal.
The palimpsest chest is on a lower level of the Lost City. So if you're a completionist, then yes after killing Montbard in the upper levels of the Lost City, you'll continue to the lower levels & reach the chest before having found the answer. But if you follow the quests, you'll kill Montbard on level 2, report to Jon Morgan, get the quest to enter Karthal, be able to find the answer, and return later to the lower levels of the Lost City. The lower levels are also *much* harder than the upper levels, so you'll probably find yourself overpowered if you try to continue in the Lost City & leave it until later - this is exactly what happened with me. You could also leave the chest until later if you don't have the answer - again, this is what I did.
I don't remember the contents of the chest actually being necessary to get into Karthal at all (and find the answer). So I wouldn't consider this a "bug", certainly not a game-wrecker.
