what matter the most is the knowledge of the forum rules
I disagree with this. Even though a person must know forum rules to be a staff but a person who know forum rules may not be able to judge the reports.
If a *person* knows the forum rules , then in this case he will be able to handle the reports. Now I do not think new moderator is needed (maybe only for the local boards, if someone of us can speak/write (fluent) various languages maybe he will have a high chance to manage that section ).