The last anecdote I heard was that they were no longer collecting the surcharges on KE (happened about the time the VA surcharges disappeared), but still collecting on some partners like CZ. If you change an existing award, they re-do the taxes/fees and it will wind up being whatever they're currently charging/collecting (and so if foreign taxes are converted to USD, you'll likely see a change in the taxes/fees because of simple currency fluctuations).