For a long time now, i could never chat after i died in a game. i would die, it would go to spectate mode, but none of the keys would function except for escape and the hotkey for using a revive. Recently, i found out how. I'm not sure why it's like this in the first place, and maybe it's only me (since until the vault thing came i never got faction swaps, ever) but if right before you die, you press T to open up chat, when it goes to spectate mode you can press T again the the chat function works properly.
This is also true for spectate mode. although it is by default hotkeyed already, i could never switch between players when spectating. I simply hotkeyed them to my arrow keys and now they work.
just a little "trick" or whatever. hope it helps.