Sigrdrifa, I analyzed computer programming from 1982 to 2001. I know a thing or two about masking and I know it when I see it. It is a common technique used to "enhance" the game by making quests more challenging, which is gobbledygook for how to make players spend more time playing. The nodes may, or may not, really be masked. If you are the only one in the zone, with a quest that needs the nodes, they simply don't spawn because you have a quest that needs them. But quest nodes can also be masked so that if a player, in the zone, doesn't have the quest, they won't see the nodes the players, with the quest, will see.