That really is pretty standard boilerplate, and necessary, from their point of view.
If they didn't have that, how many people would find similarities between things they wrote (however vague or distant the similarity) and things that got published, such that they might want to lay a claim? This boilerplate basically means, "Dude, if you post it, you lose the right to claim we stole it from you."
No, a non-exclusive, non-revokable license would be ""Dude, if you post it, you lose the right to claim we stole it from you."
your comments, suggestions, ideas, and/or creative materials or other information ("Feedback") are non-confidential and shall become the sole property of Wizards means "We own your ideas".
