Can someone clarify whether the "Extra Combat EXP Scroll" can be stacked on top of things like Mercenary's Experience or the 530% scroll? The description for this scroll says "Increases Combat EXP by +100% for 1 hour. This effect cannot be stacked (including Pearl and Loyalties items)." Does this really mean that you can't use this scroll with any other buffs that are going? I find that hard to believe, since so many other buffs give you more than +100% exp. 

Also, does anyone know if crystals and Lemoria armor will increase skill exp gain when afk skill training? 

The only ones that don't stack, are the blue-named "Extra Combat Exp Scroll 100% 60mins" you get from loyalty/pearlshop --- those won't stack on the Book of Combat. (there is an Event version and a non-event version of these)

Also, the Combat/Skill 300% 60 minute wont stack on the 530% 1-loyalty scrolls.

Other than those two scenarios, the rest should stack unless it specially says otherwise.