I'm never really sure when a topic belongs in one board or the other, because the two basically seem to be for the same thing. The rules don't make it any clearer either, because General Discussion doesn't have it's own rules and Chit-Chat just says that "if it doesn't go anywhere else, it goes here." I'm guessing that the difference between them is that General Discussion is reserved for Subeta-related discussion and Chit-Chat is for everything else, but that's mostly speculation and I believe there may be other users who would disagree depending on the specific subject. I was wanting to start a topic discussing the Subeta community and everyone's perspectives on it, so I would guess that it belongs in GD, but I'm unsure and not a fan of the ambiguity.

pretty sure you've got it right: if it's about a subeta feature or discussing an aspect of the site or community, it goes in general discussion (which is located under the 'subeta features' header for that reason) and chit-chat is for talking about other things, real life stuff, whatever - which is why it's under the 'social scene' header, which i interpret to encompass all non-subeta conversations people may want to have. perhaps this could be clarified somewhere, i.e. "if it's about subeta but isn't about something specific enough to go in any particular forum, it goes in general discussion. if it's not about subeta or something that could go in the creative corner, it goes in a social scene forum."