I don't know if i'm posting in the right area, but I can't find where to report errors in WP codex. How could I get an account to log in the codex wiki ? Or to post a ticket in track ?
Anyway, here is the mistake I found. It is in the page I18n_for_WordPress_Developers#Placeholders.
If you have more than one placeholder in a string, it is recommended that you use argument swapping.
printf(__("Your city is %1$s, and your zip code is %2$s."), $city, $zipcode);
This code is not working because double quotes will lead to a replacement of "$s" by the content of "s" variable. Single quotes are mandatory here. The correct code to use is
printf(__('Your city is %1$s, and your zip code is %2$s.'), $city, $zipcode);