The fonts used in the chat window in wow-mania (which is a WOTLK private server) do not ever change size. there is a selector allowing one to select various font sizes from 12 to 18 point. No matter where you set these the fonts are always exactly the same size.
Resize the game window and while everything else scales the fonts in the chat window stay exactly the same size ... . . . . <--- pretty close to this big to my eyes.