well, what can i say about this button "Report to moderador" – ain't gonna help – mods can't handle everything & everytime (they're just human).
believe me, i know what i'm telling about. here is a little time span example:

suggesting the solution:
restriction for posting from newbies accounts (fresh time creation – needs to be adjustable) + deny posting from specified accounts list (add the options to every moderated thread) – after such precautions attacker won't be able to continue his actions.
if this is unattainable with the help of only the forum functionality, it's possible to use automation tools, though is much more difficult for an unskilled users.
upd.
>> conclusion