There are two different stories here, sheepgirl's at #3 with "Are you becoming a Muslim" and AndrewSmith's with "What do you have in your bag?"
I wouldn't ask someone reading Arabic "What do you have in your bag?" and I wouldn't recommend it. And now that I think of it, on my commuter train the last couple of years I often sat next to a guy who spent his commute reading Arabic.
But I think there's a difference between "What do you have in your bag?" and "Police! Terrorist!" which is what OP's header suggests. I don't mind people being cautious and if they have to err one way or the other I would prefer they err on the side of overcautiousness.
