For the benefit of those not in the know, I should explain that wavy hands are the strange and unloved progeny of summit-hoppers who got fed up with people interrupting meetings to agree, at length, with things that had already been said.
The fundamental problem was that the solution – a series of hand gestures that would baffle deaf people everywhere - was worse than the problem, with stupidly large chunks of every meeting being given over to explaining that doing ‘Jazz Hands’ meant you agreed with something, making a ‘T’ shape was admonishing someone for going off on a tangent, etc. Curiously, it never occurred to people that a) this doesn’t stop summit bores from saying exactly what they want regardless until someone actually tells them to shut up rather than just glaring b) someone in a big room frantically ‘T’ing is easily ignored, and c) nodding was invented several thousand years ago for precisely the same reason as Jazz Hands, and smacks rather less of elitists filling the world with specialised political jargon.