They are 100% separate (although obviously based on threads/posts) and will not be changed to use threads/posts in the background. This is because it allows me complete control over the functionality; I can make them diverge from the core XF Thread/Post system as and when needed.But to the underlying question are posts in the group actual threads in a node or are they more akin to a post comment? If they are more akin to a post comment would you consider making the discussion portion an actual node with threads instead so that discussions in a group can populate in all areas where threads can?
Another reason actual nodes are not feasible is that this add-on would have a soft limit on the number of social groups that could be created. XenForo does not like having more than a couple hundred nodes, maybe 1,000 at most before it starts running into serious performance problems on even the most powerful server due to the way node permissions are rebuilt.
In other words; this add-on would not function on large sites if I implemented discussions as nodes. I will not compromise the scalability of the add-on in that way, as that runs counter to what I aim to achieve with all of my add-ons.
In a future version, I could look into creating a "virtual category" which would list a user's joined social groups underneath, in a similar way nodes are displayed, to be added to the node list. This is something I just thought up, so I don't even know if it's possible to do this
No, discussions cannot be moved between groups. There are no nodes, though in the future if/when I implement "sections", I would allow discussions to be moved in between sections.Can you move threads between groups and nodes?