Hi Valery,
thank you for your inquiry I am very happy to further elaborate for you.

If you have read posts I have published, you know I am on WordPress with my personal Blog and have been recommending Wordpress as a multilingual blogging platform to all my Clients. It will work fine and the Search Engines will not have an issue or get confused in identifying languages used.

With th eplugin I have developed called Blogslot, you can easliy manage an indefinite number of languages – you need only to setup with a bit of planning your feeds.

You might want to take a look at Serendipity, a less known platform that offers stability and functionality but is not that popular and certainly does not have the follow and common knowledge that WordPress can offer.

So downlaod and test Serendipity, see if all your needs are covered by that platform, and then take a look at wordPress, knowing you are home and dry with the latter when it comes to multilingual blogging.

I discourage use of any free platforms for serious blogging efforts – you’ll be sorry very soon … hops this helps and good lick with your multilingual blogging efforts