When in the lobby if a player has certain characters in their name then their chat messages won’t be displayed.
There used to be a similar bug in-game, but this was fixed.
In my case I think the problem character is either “:” or “”, for reference the name I am using is “c:\Mustang [GB]”.
EDIT: Turns out it doesn’t work with “Capt. Mustang” either, perhaps it’s the space " " character?
The similar bug was not fixed half of my chat messages also do not show in the lobby or ingame 
I think yours is a different bug, half not showing means it’s intermittent, also you don’t have any “special” characters in your name. Whereas the one I described is always in-game, but never in lobby, and I have special characters.
For the intermittent one I think the workaround was to set an FPS cap, say of 120, if that “fixes” it then it’s known.
I’ve found \ won’t display in lobby or in game, but ¬ will display in the lobby but in-game as a default square. There is also the old bug that you can’t type single-quote while chatting (brings up console).