At 20:36 the English translation says "But I don't think that's a bad thing." (the gout discussion) I disagree with this translation, I'd say it's probably closer to "But, it can't be helped." As in this case Kaneko's not gonna stop just because gout may develop. Not that Kaneko thinks in all cases gout isn't a bad thing (which is the vibe I get from how it is in the video.)
I think the spot you sometimes find in the oyster shells is a blister the oyster forms when it has a mud worm infection. Mud worms are hard to manage and prevent infection, but they live in the shell, not the meat, and even when infected the oysters are safe to consume. It’s just preferable not to break open the blister because of the unpleasant odor.