User prefers different interface language and theme

Gentlemen,
I notice these forums themselves are a kind of multisite setup.

I have accounts on two of them, and in both my
http://wordpress.org/support/profile/jidanni/edit and
http://tw.forums.wordpress.org/profile/jidanni/edit
I notice there is no way to edit any language setting.

This is quite unlike
http://meta.wikimedia.org/wiki/Help:Preferences#Internationalisation
where the user is free from the assumption that he prefers the default
interface language.

I suppose themes cannot be chosen per-user either.

You see I was trying to help my friend do all this,

http://wordpress.org/support/topic/allow-each-user-to-pick-their-own-interface-language-just-like-in-facebook

But I suppose if it is not possible even on these forums, it is just not
possible in WordPress.