I understand that, hoarding causes deflation. But as said in my example, deflation devalues real capital and that doesn't encourage investments.
The thing you fail to see is that money is a common. You're holding it now, but it belongs to the whole society because it is an abstract good, an agreement. The money you hold could be worth nothing overnight if society decides so.
So the way people saves should be the way that the society benefits more, and that's not hoarding.
Did you read/understand what he wrote? When you invest, you're investing in one company. When you hoard money, you're lowering prices for all. Sounds pretty good to me.
Money is a common... what? I assume you mean a "common good". Common goods are both rivalrous and non-excludable.
"A rival (subtractable) good is a good whose consumption by one consumer prevents simultaneous consumption by other consumers."
That does not describe money. There is not a limited quantity of money. If you think there is, then you don't know what money is.