I'm not at a machine with it available just now, but a very handy command is cvarlist. For example, join your server (or use your favorite rcon tool) and enter:
This will list all cvars that contain "chat" as well as their default and current settings. cvarlist for chat, spect, or talk (remember top put the * before and after the word - it serves as a wildcard for matching the cvar name) and you may find what you want. If not, I can fire up a test server when I get home and see what I can find for you.
Thanks man. I never knew about the *XXX* thing. I think I found the cvar "g_spectate_allow_full_chat "0"....I'm gonna try it our right now and report back what I find out. Once again thanks for the searching idea, I did try just cvarlist and cmdlist before but I looked through them all without any findings...this helps a lot.