How I can exclude a user from a specific topic or a specific forum?
tnx in advance
You can't block a person from just one thread without a plugin. If you want to block the person from a specific forum, just create a new usergroup and don't give that usergroup permission to view that forum.
I already knew, but what I find is a way to ban user in single topic, without creating a new usergroup
You can make a thread in Plugin Requests and see if someone responds.