Coming back to the video --- how is it possible that taxing gets harder if a currency is a bit deflationary?
Why shouldn't people get richer with the money they hold? Why is this bad thing anyway? If the government holds the very same deflationary currency then all taxes it ever gathered will also gain value, thus there is no reason to tax the additional wealth people get thanks to deflation.
We just have to remember that there are other taxes apart from income tax.
In a deflationary scenario, even if the rich are getting richer, wealth taxes can make tax collection look simple.
And of course, you could have inheritance tax so that after a few generations, there is nothing left in the hands of the original descendants.