I have observed this behavior quite a while, that notepad2 didn't encode : or =
for example:
http://site.com/?foo=bar
become
http:%2F%2Fsite.com%2F%3Ffoo=bar
should be
http%3A%2F%2Fsite.com%2F%3Ffoo%3Dbar