I don't know if this is a "bug" or not because it has been quite some time and it hasn't changed and it seems to be consistent across all linux systems, so I'm starting to think it's just the way it is and it won't be modified.
The TF2 chat font in Linux is too thin compared to windows. Here is a comparison image:http://i47.tinypic.com/1z4ihir.png
I took those screenshots with a bright background to display the need for a thicker font which has a thicker shadow so that text remains readable at all times. Even though most of the time the Linux font is very readable, it just doesn't grab my eye. Someone could be spamming my name trying to get my attention and I probably wouldn't notice.
and one of the bigger reasons why I dislike the current look is because it makes me feel like I'm still playing valve games in WINE.
Also, if you are someone who is getting text on your linux version of TF2 that looks just like the "windows" text in my image please let me know! I would be very interested, because as far as I can tell NOBODY has text that looks like that. Please correct me if I'm wrong.