My theory on why Pawns permanently tend towards becoming more talkative has to do with the idea that your actions in-game influence their AI. Using down on the d-pad urges them towards Guardian (yuk), left on the d-pad towards Medicant/Nexus (whichever), and etc for other actions like picking up everything in sight, focusing on enemy mages and so on -- the Pawns tend toward following the instructions you use and the examples you set.
If that's the case then I know there's been *plenty* of times that I've been picking up loot and the Pawns'll come dashing up close, rubbing themselves against my side like hungry, flea-ridden stray cats and, instead of pressing B to pick up, I'll instead find that I've just pressed B to hear yet another riveting nugget of fresh fortune cookie wisdom.
In short, if you talk to your Pawns, even accidentally, they'll begin to believe that you simply can't get enough of their endless supply of insightful commentary.