When I was young, I took religious classes.....
One of my religious teachers told me that it was a sin to laugh
openly at any time because 'that's what the devil does'..... that
was what she really said....
So why did I sometimes see her LOL while chit-chatting with the
other teachers? Sheesh. 
Anyway, later on I read that the consensus among religious
scholars is that there is nothing wrong with laughing, for it is
just a normal human trait.
The only caveat is to not laugh at inappropriate times like
prayers and funerals.... neither should you laugh so loud to the
extent that you disturb and annoy your neighbours.
That makes a lot more sense, no?
I don't think that has anything to do with religion ..... that's
just basic courtesy ! ....
