If you look at the raw IL (from ildasm, not the C# equivalent via IL Spy), that may help you see what the decompiler is trying to say. 'Out' parameters are represented using a (managed) typed-reference, which isn't explicitly exposed as a type in C#. 'Instances' of this type can normally only be passed as parameters to methods accepting typed references ('ref' or 'out' parameters.) See OpCodes.Mkrefany for more information.
What dotPeek is complaining about is that this 'out' typed reference was stored from the argument into a local variable slot, then written to later via the local slot. The '@' and '^' are placeholders used to indicate this unexpected behavior detected by the decompiler (the one the ISSUE comments describe.)
It's possible the code was compiled from C++/CLI and thus the IL looks different from the typical C# compiler output. It's also possible this is some level of minor obfuscation to confuse decompilers (though I don't think so.) I don't think this is functionally any different from loading the reference from its argument onto the operation stack directly (avoiding the use of a local variable slot), but I could be wrong.