I gave up keeping up with the playtest largely to avoid Beta Burnout. So if they're talking more about professions, it'd be nice if they called them "professions" instead of "traits".
Traits are the term they used to describe abilities for the "interaction" pillar. Every player gets to choose a background that (right now) appears to include three skills and a trait. So far, the backgrounds we've seen are knight, priest,
soldier, commoner and sage. Those five backgrounds each come with a trait: Knight’s Station, Temple Services, Endurance, Trade or Researcher. They provide a minor ability that's appropriate to the background.
I like that the traits are flavorful and not unbalancing. However, I don't think they do enough to differentiate the characters as they interact with the game world. The "Knight's Station" ability just allows you free food and lodging where people recognize your status. In the games I've played (at least the good ones), that is a pale shadow of the social benefits of knighthood.
I don't claim to have the full answers. Obviously, many background benefits will be highly campaign specific. If you give a noble the full benefits of nobility (status, wealth, contacts), it's hard to balance that against any reasonable benefits you could provide a blacksmith or a local criminal. I'm not sure if WotC should punch up the benefits or just provide guidance to DMs who want to.
The Social Favored Terrain idea is more focused on a specific problem: if you just rely on attribute and skill bonuses, a small number of PCs totally dominate the "face" aspect of interactions. If that's supposed to be a "pillar", then you want the mechanics to support characters taking advantage of the social connections of their background.
I don't even know if you need to create individual "social terrain" modifiers for every single background... you might easily just have a rule in the front of the Backgrounds chapter (or within the DMG) that says that interacting with others of a similar background automatically grants a +1 circumstance bonus to social skill checks, or that you tend to default to Neutral (if not) Good reaction to NPCs of a similar background. It could just be a more universal rule.
Yeah, definitely. But it would be useful to provide some guidance to how broadly the bonus should apply. Do knights get the benefit in the high status context
and the military context? Also, some backgrounds (Charlatan?) might have a special version of the ability that, to pick that example, could provide a lower bonus to a wider range of situations.
-KS