This one doesn't really need much explanation. Just watch the video to find out what the 'Tesla nod' is:
If you are a Tesla driver, or have been a passenger in one, have you noticed something of the sort take place? A kind of acknowledgement between Tesla drivers? Like members of a club doing a secret handshake... I know the same thing used to sometimes happen in the early days of hybrids, a kind of silent "yep, me too".