Only the individual forum owner can add a moderator. If the forum owner is letting these things go, there are basically two options.
2. Add a moderator or three to police the forum and save it.
There are other options, but the owner seems to be MIA over there. Here is another option for you.
Create your own forum and invite users from that forum. Before you invite, make your forum a "members only" forum. New users will have to apply to be in your group, which you will give posting rights. All other users can be made post-moderated or read-only. This will pretty much eliminate your troll problem. You may get people who register, then cause problems, but then you have the option to remove them and end your problem with them.
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