Right now the only way to determine if an NPC gives quests, is to click on them and wait for a response in chat.
Is there anyway you would be able to put some kind of special marker or display on the NPC to signify that they do have the Quester Trait?

Some of the players on my server also play World of Warcraft and we had a decent conversation of how nice it would be that the NPC's had indicators over their heads like WoW does. I know that putting a ! or ? over their head wouldn't be possible, but perhaps something to signify they are indeed Quester NPCs?

Change name color of quest npcs.