In my opinion the kilt is an alternative to trousers (pants) and can be dressed up or down as the wearer likes. Like trousers (pants) they can be worn on formal and informal occasions the only real difference is that one tends to change ones trousers to suit the occasions whereas a good kilt can be used for either. If worn as day wear then I feel almost anything goes but when it comes to formal occasions then I would like to think that tradition comes to the fore and common sense prevails. I doubt if anyone would expect to get away with wearing trainers and jeans with a dinner jacket and bow tie to a formal occasion. (I may be wrong) I feel the same about the kilt attire and it should follow some sort of general rules for formal events.