I whistle subconsciously, so have probably done so on a train. I often don't really know that I am whistling until I'm told: I can hear it, but it doesn't translate into a message along the lines of, "You are whistling. Stop. Now." I occasionally whistle a tune (which sounds tuneful in my head, so is tuneless to the listener, as with most whistling), but more often than not it's something I make up on the spot - I call it an experiment, you may call it what you wish

The long and short of it: were a ban on whistling to be imposed, I would probably end up falling foul of it without realising. Judging by the amount of posts on here that detail a dislike for whistling, I think it might be prudent if I steer clear of any Forum Meets...