It's a important part as well, but I don't get what I want exactly.
I can control permission on the whole page forum, and i want to control permission on thread of forum and reply thread as well :
User1(Can view all, can post new thread, can reply to threads) User2(Can view all, cannot post new thread, can reply to threads)
do i need to custom default webpart? and how? Could you please provide me an other solution?