He's not trying to eavesdrop. He's very specifically trying not to eavesdrop. It's simply that, in this instance, he would need to be deaf.

It's a little worrying, actually, what they're talking about. The hushed conversation implies that Vervain knows there's a reason Tuo wouldn't get on well with a shepherd, and Tuo's reply is quietly alarming. Does Vervain know where that homeland is? Does someone directly associated with the church now know where Dain comes from?

He wants to trust Tuo's judgement, but against a decade of caution, that desire rings disturbingly hollow.

"I take it you two have met before," Dain says, looking up from his somewhat fruitless feather-gathering task. Maybe he heard their conversation, maybe he didn't, but he certainly doesn't feel strongly about anything in it, if his idly curious tone is anything to go by.