Inflation and changes to the money supply are not the same thing. This conflation gets pushed by libertarians/techno-libertarians constantly. The money supply can increase and inflation (the price of goods and services) can go down.
To inflate = to increase in size. The money supply increases = it inflates.
That is a disingenuous argument, at best. Inflation is a specific economic term with a specific definition. And it's not increase in the money supply.
That's correct, and also prices increase (or inflate). The parent is saying conflating increase in prices and increase in monetary supply can be incorrect.
Sure. However, the problem is the increase in the money supply, which is theft. The increase in prices is rather irrelevant - inflation would still be bad even if the prices were to decrease. (There are hundreds of papers explaining why.)
How is an increase in the money supply theft if increases in price are irrelevant?
The same way debasing gold coins is theft, even if the prices don't rise (because, say, you just conquered another country and got a new bunch of slaves to produce stuff). Claiming that inflation is a rise in prices confuses cause and effect.