There should be "invisible" state like in every normal chat outside this environment.
It will:
1) make useless all spy efforts
2) add some privacy to each player separately (because if we speak about invisible state we also speaking about "afk/busy", "chatmode" and "ingame" states)

My personal opinion as new member at this community: Players shouldn't abuse this not intended ingame features (lets avoid word bugs here) to do recoinassance work. They should use detector/masked e-war bots for this job more frequently.