It takes only about 10% of nodes to somewhat reliably propagate a transaction. Even fewer are enough if they preferentially peer like Libre Relay does (TIL!). So, yes, it’s not effective.

Censorship, stifling information, is always more difficult than spreading it.

So in other words... attempts to 'filter' transactions successfully by running a client with 'stricter' mempool policy than core... is pretty much hopeless?
????

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Also important to mention: Libre Relay automatically peers with other Libre Relay nodes. So even with only a small minority of Libre Relay nodes, transactions still propagate reliably.