I’m pretty sure the /en is still needed - the way the translate extension work is that every “base” page (https://www.whonix.org/wiki/Lantern) basically becomes a symbolic link to the base page + “/[user’s configured language]”. If we delete the /en, English users will be rather cross I bet.
Actually, that is not the case. Only for languages, other than the used base language is a specific suffix needed. We just have /en on a few sites because of an old, small issue in which, once someone called the translation extension for a certain design, it created a separate site to translate to English, as it is the standard language. Wrote this somewhere already, I think.
Like Patrick said /en is superfluous.
Have a nice day,