Update: For what it's worth, text also renders very differently between the editbox and the chat window. I see no reason why this should be the case for any font.
Certain characters (especially fullwidth characters) appear larger and wider in the editbox, and right-to-left text markers function in the editbox but not the chat window.
I know the likely response is "it's the font", but how is it possible? Why would there be such a difference between the two text fields?