Some parameter names in IronPython have \u00F8 in them. This is a legacy thing, as described bu DinoV:
 
"This is a bit of a hack... It's there so that "args" is not accepted as a keyword argument.
 
Because \u00F8 is not a valid identifier in Python there is no possibility that the user can
provide this as a keyword argument. We ran into some bug I believe back in the IronPython
1.1 time frame where someone was trying to provide args as a keyword arg and this was a
quick and easy fix. A better fix would probably to add some [NoKeywordArgBinding] attribute
to the parameter and then update the overload resolver so that we don't allow binding of
keyword args for that parameter. And I suspect that will become necessary for Python 3.x
support where I think you can have Unicode identifiers (even though this exact identifier
is unlikely to be used :) )."
 
Having the overload resolver ignore ParamDictionaryAttribute and ParamArrayAttribute is a big win (since those would never be called by keyword); adding NoKeywordBindingAttribute would get us the rest of the way.