I'm not happy about wild cards. It seems like taking what is a very powerful character in software development and using it for a pretty minor usability improvement. Besides it seems misleading. When I see an asterisk I don't think throwaway. I can see how that aligns with "anything can go here" meaning from regex, but I feel there is a difference in "value". Using a * in a regex seems to increase the power and heft of the regex, where as using it here, seems to decrease the value, which is almost the opposite effect. Another way of putting it is that the point should be to let me ignore this while reading code, but the asterisk draws my attention to it instead.
Compare this to the Haskell convention of using an _ for throwaway items, which disappears just enough, instead of attracting attention. And by simply being a convention, it isn't giving the character too much power.
Not sure if lack of Haskell style type inference prevents C# from using convention for throwaways instead of wildcard chars, but I think it would be much less overhead on the Dev.