block function, seriously, i played Xcom EU online, and there was no way you could mute their mic, or chat, so if they wanted to fill your screen with crap, or breath heavilly down their mic you would just have to put up with it. Same with Wargame EU, no blocking the chat. Don't do this, put in a block function.
I think Mumble will be the de facto voice communication standard in PA, and it has a very nice muting system built in. Muting text messages would be very useful though, because somehow there are always chatspam griefers.
All good and fine, but since Uber already has a Mumble server going for SMNC, it seems like that would be their first choice for a 3rd party voice app. Besides, the licensing is more open, and it has better cross-platform support, so Mumble is probably the best starting point for Uber's voice system. And since the UI for PA will be very configurable, adding in Teamspeak/Ventrilo components shouldn't be too difficult.
Hm, one of my arms has a nanolathe on it for building massive planet destroying armies and other arm has a super powerful gun on it that can blast anything to bits in one shot. I wonder which one I could use to stop another commander from annoying me with chat messages... But in all seriousness a mute function is pretty easy to add to a chat client and I doubt Uber will overlook it in the final production release.