We got a ton of feedback from French speakers that they preferred the English content, so we ended up settling on selecting a UI based on the A-L header but giving the default English content (unless you specifically set it otherwise).
In any case I think that if you really wanted to target the French-speaking population, it would be best to have a separate site or at least a clearly separated part of the site.
There's one for every supported language.
It would be a different story if the content available was comparable, but it usually isn't.
The French consumer market has tons of holes like this. And we're talking about a huge, wealthy market with plenty of mobile devices and solid broadband. It's not a wide-open market, but there are tons of opportunities.
I'm hearing more and more about French startup accelerators, and I'm seeing a lot more seed-stage startups. So people are making an effort to serve this market. But there's still a lot of opportunities.
Was there a particular social forum that ruled minitel - did it transition to the web?
Probably a strip of language names along the top, taking you to language-filtered frpnt-pages would help. It would be ugly, but it's Reddit.
That said, http://fr.reddit.com/ should be the top posts from the French-language subreddits, not just the main frontpage with a French UI.
It's still gread that they provided a multilingual UI, but as a whole, us companies could always use to understand the foreign market a little bit better than just providing a UI translation...
To give you an example: there is no reddit equivalent in French. The closest things we have are a few French-speaking subreddits that have very few subscribers since reddit scares people who don't speak English before they can reach the French-speaking subreddits. We also have a few very poor quality reddit rip-offs with no users.
Granted, the French-speaking world is not as big as the US market. But 100 million people is already a decent target, don't you think?