Localize string inside chat area (from your example)

[pcutile]

I put a string inside a chat area, but i can't localize it, all seems correct i set another language and string inside chat area is converted right, but when i scroll with scroll bar string return in first language.

[ArenMook]

You need to localize your text before adding it to chat. It doesn't make sense to localize the chat's contents on the fly.