Avraham says:
OOOOooooh. That
is cool. I mean, if you're a depravedly wicked DM, I mean. Of course. Nevermind. /me whistles innocently.
I could see you guys using that with each other as well. Perhaps one of you whispers something to another, or gives someone a
look surreptitiously. You can make it look absolutely clean on your screens, and since I'm aware of it, I can roll Perception for everyone else and only make the people who pass the threshold informed.
(Side note, I don't suppose it much matters to you guys, but I don't believe in Passive Perception or any other passive skills in PbP. The spirit of it, far as I can tell, was to not have a physical die roll at the table tip people off to things, and in PbP that's a nonissue because you can't see me rolling anyway. So for better or for worse, you always get rolls. And then if you ask for/make rolls on top of the one I made for you, I just go with whichever one is higher, so it's like you give yourselves advantage by consciously being on the lookout.)