rabadi you make it way too complicated, all you would have to store is the users that are actually banned from the thread.
However while it would be possible to implement thread banning by altering the php files and adding an extra table between the members and the post table we won't bother with this. It would just be a waste of time, and since php files would have to be edited possibly even introducing bugs or security leaks (we wouldn't want to jeapordize the main site, would we?).
When the moderator feels a thread has lost his original purpose he closes the thread it's as simple as that.
Another reason to lock a thread is when we feel an answer to a question was given.
I will lock this thread since we won't implement thread banning.
