Weird--I had genuinely never noticed anything related to dirty socks in miso soup, even the generic stuff you get in cheap US restos. It just tastes salty and tasty to me. Now I'll have to go downstairs and make some, and see...

The dirty-sock element I guess comes from the fermentation? I wonder if the people here who don't like miso soup also aren't so keen on soft-rind cheeses, or kombucha, or sauerkraut, or any of the other rotting-but-tasty culinary phenomena?

Or does the bad taste come in from boiling it? I know you're not ever supposed to boil miso. (And you're also not supposed to make green tea in too-hot water--that's when that nasty fishy taste comes in.)