@trwnh
I'm not sure I understand that question, but...
Perhaps the way to think of this is that the client should have some indication of whether the post should be threaded with replies or not.
Quote-posts probably should not be -- they're the head of their own new thread.
Of course, the client will actually make this design decision, so we're just hinting to it with the data structure.
(Perhaps the OP should have some way to find those, I guess, but it shouldn't be a default).