Currently reshares are getting their own GUID and thus they are treated like independent posts with separated discussion trees. This often leads to parallel discussions.
AFAIK there had been plans to change that - how far are they developed?
Additional thought: It would be great having two different options. One would be a traditional reshare - but keeping the discussion tree. The other would be some quoted reshare where you would perform a reshare with an included comment. This should then create a new post.
In fact the latter could be done by adding a new field to the existing reshare that then would contain the comment. What do you think?