nah thats foolish, if you hide posts on purpose then you're losing the conversation thread, and threads may become chaotic (like people talking to a wall) because many people would be using this ability. A thread would go (apparently) offtopic for a general viewer.
It's like people walking in the streets wiht the headphones on and having a telephone conversation, I often say they are bad of the head, and old grandmas agree with me, because for the rest of the world they're talking alone.
You want this for Ic?? do you really think Facebook should be a ezample to follow??
Nah, pls dont ruin the forums, if you want private converstations then use a chatroom, if you dont want to see others people posts just ignore them. But you always should be able to read everything from everybody to give a proper answer in the thread, otherwise, as told, it'd become chaotic.