Re-read the post: there was no suggestion of practising incipient spinning without being trained in this. The scenario posited was that of a diligent PPL who has been trained in incipient spin recovery, and who, just as he practices forced landings, sensibly practices getting into potential stall/spin situations. Suppose that one day he bodges his recovery and spins. He has never spun before, still less recovered. Good luck to him.
There are, as far as I am aware, relatively few accidents during spin practice. Spinning accidents seem to occur during low-level deliberate naughtiness, and following inadvertent loss of control in sitiuations such as forced landings (I agree with all above who emphasis the need to recognise and deal with incipent spins) . Avweb has a thoughtful article on this:-
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www.avweb.com/news/safety/181570-1.html
I don't think anyone is suggesting that everyone should be obliged to go spinning a lot, or to spin solo, or that if you don't spin you are not a competent pilot. I would say, however, that exploring the aircraft's behaviour in all regimes of flight may make your training more complete. It may also be a comfort to have it demonstrated that the system does work. Many things in flying do exactly what they say on the tin: : if you apply dead reckoning nav, you will get there, if you set up your PFL correctly, you should get into your field. If you spin a typical trainer/tourer (which is allowed to spin on purpose) , it will respond to standard recovery procedures (always allowing for some oddity of trim etc and the fact that spinning is never 100% predictable). Aircraft which are not certified for deliberate spinning cannot read their own placards and are capable of spinning and of recovering from a spin. Shouldn't the pilot be likewise?