There are also ways to farm Merit Points so the Mods/Merit Sources have to be careful, here is just a scenario:
You create 10 accounts, then you start spamming with all 10.
You report all the spams accounts you created from your main account and there you have Merit points for reporting spammer.
There always be someone trying to cheat the system unfortunately, so Admins and Mods have to be aware of this.
Did I miss something, Is there Merit reward for reporting spam posts?
No, you do not earn merit by reporting bad posts. Just another sig spammer posting bullshit on topics they know nothing about - exactly the sort of thing this new system will hopefully discourage.