Forum visit rewards.

I'm not talking number of posts. I don't think anything in the game should be tied to number of posts on the forums.
But simply joining the forums, I think that's a great task...

Making a task for people to visit the forums will bring some people to the forums, but the majority will just come, register, and then never come back again.

There's plenty of point systems that can be applied to these forums through MODS and linked in game. That part isn't hard to do considering all accounts made are also made on here.

The best way would be for a reputation system or something of the sort. Reputation could be removed from players by mods if they're negative reputation just for the sake of being a jerk.

There could also be a "Like Post" MOD added as well. You can only "like" 5 posts a day and you can like the same post more than once.
It would probably do to make it so you can only like a specific users posts once a day. Meaning if you like User A's guide post, you can't like User A's suggestion post in the same day.