[lovemenot]

I did not mean to imply that slower trains such as Hikari or Kodama on that route might make one nauseous. Rather on very rare occasions, a too-slow train would let you feel the side-to-side as it banks.

Well anyway it seems to have been just a one-time experience, from which you've managed to deduce both generality and cause.

Again, from experience that's not common, so perhaps a more charitable explanation than system degradation might have been warranted. Certainly the rolling-stock is much newer than the system. The Nozomi you used would have been, at a guess 15 years or younger.