I recently played on a modded server, and after fixing the usual annoyances that come from doing that, I discovered that I could not see what I was typing into the chat interface unless it was at the end of the game while the scores/stats were showing. After some searching of my multi-player .cfg files, I discovered an entry that with some tweaking fixed the problem. So here is the short version:

Open your game. Before entering play, open the console (you must have the console enabled first in the game options) by typing the tilde, it looks like this: ~

Just press the shift key and the button under the Esc key.

Now type "cg_hudChatPosition 5 204" without the quotes. Restart your game, and now the chat thingy will be fixxored.