I've just moved on to the sign-post on the risen road, and during one of the regular ~10-20s freezes I perchance caught one of my party members exchanging dialog with someone else.
I don't know if this is some quirk of playing in an ultra-wide resolution (2560x1080) but after spotting this I went back 15 saves and spent a while walking around. Low and behold, it almost seems like going off screen is a trigger for dialog.
It also looks like I've missed a ton of perception/history/arcana/etc rolls because they went off screen and - when I noticed something had happened - wasn't able to snap back fast enough, so figured it was just a glitch.
Is there a way to get better awareness when stuff happens to / between random party members? Highlight a frame, a short-lived badge, something. I'm guessing this would have made the party seem a lot less like an after-thought that I have basically ignored outside of combat (and sometimes inside of combat because the fight is often over before they catch up and manage to join combat)