This is my setup:
1. A node that is available only for people who purchased an upgrade. Users can only see/post in their own thread.
2. These people have special user group that they put into when they upgrade their account. This user group have the forum permissions to view only their own threads, post their, etc`.
3. When trying to check their permissions through ACP, I can't see a thread that they've created in that forum.
4. When logging into their account (with username and password, as usual), I do see their own thread.