Multilingual site like stackoverflow

Multilingual site like stackoverflow

I've spend a couple of days thinking of a best practical way to build a
multilingual site like stackoverflow, where all users can post their
questions in different languages taking the following points in
consideration:
The website has a home page were the questions appears, (like stackoverflow)
It is language wise, it means, users who speak language X don't see
questions in language Y, unless they want to. They don't see other
language unless they choose to browse all questions in all/specific
language(s).
I have thought about many solutions for this, such as:
To let the user choose the language of the question or his country while
posting it, but I don't see it feasible and it can be very boring.
To have a sub-domain for each language, like this answer here Building
multilingual site, but this will not give a realistic visit number to the
main domain (www.example.com).
I've looked into social networks, like facebook & twitter, who let the
user to decide which feed to read on his wall, which they can in any
language, but that is far from what I want. I don't want the user to
choose, because that will lead me to create groups, and eventually it will
turn into another social network.
So, I'm wondering how can I manage to create a multilingual site but like
stackoverflow taking in consideration the points above?