My 2.1 Kendas state 40-60psi on the sidewalls. To me 40psi sounds like the high-end for mountain bike tyre pressures but presumeably the manufacturers know their stuff so what is going on? Is there some obscure EU tyre test that requires high ratings to comply? Should we be pumping up tyres harder and setting suspension differently to compensate? Any thoughts? (Other than really fat blokes stating that they need 50psi to avoid pinch flats 😈 )

It’s because of sidewall flex.. Lower pressures make the sidewalls flex more, so they are more likely to wear out quicker. Eventually the threads separate. I’ve had a habit of running tubeless tyres at silly pressures, and you can see the threads starting to break apart on old ones. Unless you’re in the habit of running your tyres until they are bald, I wouldn’t worry about it though and run what you want