[QUESTION] 1.12.1 and names of characters in cyrillic

[PRoToRiaN]

Hi guys! Please excuse me, for my google-translate language  

I'm trying to make so, that the players, playing in Vanilla, have the opportunity to create characters with russian names.
After a series of tests with the core server, i came to the conclusion, that not only server check the names, it also makes the client. I'm trying to encode Win-1251 in UTF-8. It was useless. Apparently, the check, located inside the client, rejects absolutely all the symbols, that go beyond the basic latin.
By my calculations, name checking happens between

Code: [Select]

function CharacterCreate_Okay()
PlaySound("gsCharacterCreationCreateChar");
CreateCharacter(CharacterCreateNameEdit:GetText());
end
And

Code: [Select]

void WorldSession::HandleCharCreateOpcode(WorldPacket& recv_data)
{
std::string name;
recv_data >> name;

~
~
~
}
But where, how and what are the conditions of this check.. I can't imagine.
I think, that in this situation, need to dig into the main executable WoW.exe.

Unfortunately, I hardly know this area, and therefore ask something to help me in this matter.
Or maybe I'm wrong and the problem is elsewhere.