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Great question. the salt is not there for the taste of salt. A pinch of salt helps with the ionization process so your taste buds can pick up the tsate of the chocolate, ice cream, etc, better.
I think this was discussed in an episode of Alton Brown's Good Eats as well.
It enhances the flavour of the chocolate, vinegar is used in a similar way when added to cream sauces and mousses. We use vinegar to bring out the flavour of aubergine in our mushroom and aubergine sauce. Worth a try! :)