Radio chatter and having to listen to sometimes un-needed bits of information is part of being a Squad Leader.
Much as I would like there to be some magic filter that only let me know when a report was relevant to my Squad, I recognise that it's my duty as Squad Leader to sort it out myself and use what information is available. Essentially I AM that filter, my job is to relay the relevant stuff to my guys so they can use it to better their position (and fun

).
I would much rather be on a server with frequent talking on SL Channel and VOIP and local Mumble than on a server where nobody talks. it's basic teamwork, too much information from entheusiastic players will beat not enough from players either lonewolfing their squad, or too afraid to break the silence.
There are only about 9 SL slots.. If you are a regular and good SL you will learn the other players, and you will use the last 20 years of human interaction experience to know when and when not to talk.
If someone is being a loudmouth generally other people will back you up if you tell them to leave it.
Also, on the annoying local chatter - If some guys are being asshats, it's almost always because nothing is happening - I.e. you're all at a cache not being attacked (but needing to be defended). Sometimes on PRTA that happens, and it will usually annoy me, but I ignore it. It's an inseperable part of the high level of comms Mumble allows and as such I can tolerate it.
Really, muting everyone because it infringes your dome of security (being able to deal competently and confidently with lots of different comms at once) is pretty lousy in my opinion. And if some of it is too much, just tell them to shut up as more important stuff is going on. Works for me anyway.
Sometimes I think I talk too much on Mumble.. But nobody's told me to shut up yet.