OK, I read the linked article now and apparently you have to change a setting in Firefox in order to see the URL in punycode as Mozilla decided it is "not a bug

OK, I read the linked article now and apparently you have to change a setting in Firefox in order to see the URL in punycode as Mozilla decided it is "not a bug". Eg. about:config and set the "network.IDN_show_punycode" to true to avoid this trap.