Decoding %25 may lead to URLs that contain %foo where foo is a random string, e.g. %25abc -> %abc.
Such URLs are rejected by some sites (github.com returns 500 or 400, e.g.).
So we don't decode them from now.
For testing: https://github.com/ilyaigpetrov/copy-unicode-urls/wiki/Test-%25-and-%3F.