To me it would be simpler to keep up with by setting troublemaker permissions the same as user except for post moderation and then delete the member from users.
Of course I don't know the whole picture of what you are trying to do with all of your groups.
I did, I used the Copy option to make a duplicate of User Permissions into 'Trouble Maker' group. I then did as you say and just changed the post moderation. Unfortunately this didn't work. I then tried to delete the poster from the User group (leaving him in Trouble Makers) and then they couldn't even see the forum etc.
Thanks anyway Ruben .. It’s a tough one and non-intuitive.
I’m kind of surprised that the ability to moderate particular poster’s posts is so complicated / impossible.
I run a gaming site and I periodically piss off the gamer community by making changes they don’t like. I hate to ban them, so the ability to moderate their posts until they cool-the-hell-off would be the best option.