it would be great if you could bring part of that discussion in here to make it more open, but i understand if that cant be done
id be weary about having ingame item rewards for posts and for simply joining the forums as that could just lead to more spam and un used forum accounts
you could try some sort of poll system where each week, players vote for the top poster of that week and they receive some sort of reward, like a hat or an ec
you could even try having several catagories like funniest, etc