Yeah, that's a good thing. Five so far, yeah, might be a few more. But I guess any who don't know it and would want to learn, some of us can try teaching it and practice. I think that's what they did when in school during the second war, it was a secret group called Dumbledore's Army. To learn, improve, and fight back.
They also used coins with a Protean charm to talk to each other for urgent stuff, I think. If that's decided to be used here, I have a handful of galleons that I can donate for it. Though there's always phones or these boards to use, but maybe an extra method can't hurt.