Before I go in and role my own solution to this problem could someone please confirm that there is no current way to reproduce the old threaded view in Telligent Community 6 & 7
It seems the architecture is there with ParentReplyID being stored in the database, there is a migration bug that means that old posts have an incorrect value in this field. I can work around that issue but the real problem is that using the call $core_v2_forumReply.List there is no way to get only the direct descendants of the thread. If you pass 0 in as the parentreplyid it gets all replies and since the first level have a parentreplyid == 0 this is a bit of a problem!