The template prints out the root by itself

Right, the template is where the duplication of the root is, since now the root is just the first "descendant" in the tree.

brutaldon/threadtree.py

@@ -29,7 +29,6 @@ def maketree(mastodon, root, descendants):
                   descendant.in_reply_to_id,
                   descendant.in_reply_to_account_id)
     seen = set()
-    seen.add(root.id)
     def onelevel(reps):
         for rep in sorted(reps):
             if rep in seen: continue

brutaldon/views.py

@@ -699,7 +699,6 @@ def thread(request, id):
         {
             "context": context,
             "toot": toot,
-            "root": root,
             "toots": toots,
             "own_acct": request.session["active_user"],
             "notifications": notifications,