Suppose you choose node permissions.
Select the appropriote forum
Then select usergroup "moderating"
Then scroll down to "forum moderating permissions"
Set "Manage (move, merge, etc.) any thread" to "no" for that specific node.
I presume in this case the Yes for the Moderating usergroup overrides the specific NO in this node permission?
Or use the bottom option and use the "user with permissions set" option? Put the moderators name in there and explicitely use the NO there?
Because that NO would override the inherited yes from the node permission?