i (try!) always (TO) nod at others on bikes, or thumbs up if overtaking another on a bike (left hand obv) and do the hand, foot thing when over the water, (as with you sharky, even to plod)
but was amazed when (after a previous day out with same group of friends) one of my friends, friends (you get the picture)
took me to task, as i had the stupidity to take my hand (left) off the bars to wave, to said friends, as i continued (making progress) along the dual carageway as they peeled off and i continued.
i was traveling in a straight line, and he said it was irrisponsible!
(he is an advanced instructor)
do centrapiedal forces and gyroscopic effects not apply if you wave?