The requirements sound very reasonable, the four hour limitation should stop people from randomly trolling however the requirements will not put an end to well planned trolling, however this is an unfortunate fact of the Internet and trolls that have no life will generally go as far out of thier way to troll as is needed. But here's an idea, perhaps make people donate a satoshi to get into the forums? That would demonstrate an ability to use bitcoin, although setting up that system may be tedious.. Never mind the way you have it is good too.