What set me off on this trail of thought was probably John Foley's much-viewed (and much-commented-upon) article for the Sport and Recreation Alliance (and Chessbase, and CSC) which among various questionable claims, like those relating to Alzheimer's or Caxton*, says this:
Players are penalised for poor sportsmanship e.g. for refusing to shake hands with their opponent.
This may be right. It's possible it's right. But is it right? I'm not sure I can find anything written down that says it's right.
It's certainly sometimes right. If, you instance, you read the competition rules for the 2013 World Rapid and Blitz Championships, you can find the following at 6.10:
That seems straightforward enough, superfluous and in the second sentence notwithstanding. Of course the rider about "after being asked to do so by the Chief Arbiter" was among the memorable aspects of the Short-Cheparinov incident seven years ago. That particular ruck could not have happened without the Presidential edict from the year before which introduced much of the wording above - but not the part about the Chief Arbiter, which clause was the basis of Cheparinov's appeal and...yadda yadda yadda. Let's not go on. I'm sure you remember the incident and if you don't, you can read some more about it and even view the incident below. What larks.
But that was in 2008. What has happened to the edict, or the rule, since then?
If you select and Google a section of the first sentence from the wording above, you'll find a few hits for FIDE events - like the 2014-5 Grand Prix - but none of them will be for the regulations governing the current World Cup (which, like Ian Nepomniatchi, you may well have looked at already in recent days). Nor those drafted for the 2016 World Championship, nor the current Laws of Chess, nor those that were in force until July 2014, nor the general rules governing FIDE tournaments. Not a sniff of a shake, indeed.
So what gives? Was the compulsory handshake (or, indeed, normal social greeting in accordance with the conventional rules of our society) ever part of the laws of chess as such, or was it just a regulation temporarily in force between official revisions of those laws? Is it in fact still applied by arbiters, still assumed to be implied, by past events if not by the actual letter of the law - or has it been dropped because for one reason or another it is considered unnecessary or unenforceable or for some other reason?
Do we have to shake or not? If so, who says so and where? If not, when did they stop saying so?
[* (neither of which have been amended when the article has been reproduced, so I assume Mr Foley is sticking by them]