Similar to how the testing server has a feedback forum, the normal game should have a feedback forum as it it is continuously open and receives new content.
To a certain degree, the general discussion forum meets this: there is no pressing need for a universal feedback forum. Devs and admins can see the positive and negative effects of an update, quickly find bugs due to the huge player interaction, and see what they did right with how much people are enjoying the update or particular features of it.
Positive feedback is also a powerful too, and I think finding out what works instead of relying on suggestions forum for what the game needs/lacks is a better indicator for how to proceed with the game development and administration, rather than a generic 1-5 enjoyment scale survey at the end of a spiralknights session.
We already have that.