I keep hearing about these dialogues between, for example, Eder and Aloth, but so far I haven't heard zip.
However, I did witness some snark between Hiravias and other party members. But it seemed to happen when exiting the inn in Dyrford Village, not when just walking around.
I'm curious whether others have discovered banter triggers in specific areas, or after certain quests have been completed, XP accrual, or time. For example I know there's some barks when you cross major milestones, such as after meeting Maerwald (which also triggers some "one on one" conversational requests), but I am more interested in the meant-to-seem-random inter party banter.