That's not a bad idea.
The wiki is a valuable resource, but a chore to create and edit. It's unrealistic to think you will get quality content added to it regularly if players aren't getting something out of it. The bottom line is that this is a video game. The people that play here are here for just that: to play. It's the staff who have an interest in building and governing the world, but even for them something like this would be considered tedious.
So, in short, wiki's can be very valuable, but if you don't make it worth while to create it, it just wont get done. With this being a free a shard, I'd say it would be a bit unreasonable to ask staff to pay someone to do this out of pocket, but perfectly reasonable for them to do it with in game items.
Aside from that, it evens the playing field a bit. Not everyone can afford to donate money to the shard, which puts those who can at a slight advantage. Anyone can add at least a little something to a wiki though, so that makes donation incentives more fair. It gives those who can't donate money the opportunity to donate their time and receive a little 'thank you' for it...