Is there really no way for Viart to tell the browser to switch encoding basing on selected language or at least all be unicode? Is this coming in the release to come?

P.S. at least please, let me know if this is fixed somehow in a paid version, which I want to invest into, but if my visitor clicks on "german" and gets [] instead of all special characters and my russian visitors gets ??????? ???/ ? ?/ instead of words, that's just not very cute.

Yes, you can set the encoding in the Languages settings.
 
Go to: System Administration > System Static Tables > Languages
 
In the language table, click on Edit Messages by your language. Click on "messages".
 
Edit CHARSET to whatever character set you need, or utf-8
 
Now, all the characters will display correctly.