>When I request http://example.com/?Open, what response do you want to send me?

301 to /: this would do the canonicalization,
> location = / { if ($is_args) { return 301 /; } }

404: this would correspond to reality,
> location = / { if ($is_args) { return 404; } }

However, if one compiled nginx without the scripting engines, shouldn't it return 404 by default,
instead of returning 200 while ignoring $uri's content?