[apo]

Is there data on what percentage of cryptocurrency transactions are "Real, actual, humans buying and selling real, actual, things or compensating each other for their ideas and thoughts" and what percentage consists of "traders shouting at each other in the echo chamber"?

Exchanges use off-chain transactions. When you see a transaction on the block chain, it's very unlikely to be a settlement between two exchange customers because it's far more efficient for the exchange to settle on its own private ledger.

On-chain Bitcoin transactions incur fees. Aside from a group launching an attack on Bitcoin, there's little return for the cost of spamming the block chain.