Leaving all messages unacknowledged doesn't break chain

There's a client mod going around that just treats any incoming player message as unacknowledged (as if the sender was blocked or the signature invalid when only showing valid signed messages), thus always keeping last seen signatures empty while still keeping valid message signatures on the messages you send out. Since you could in theory just have every online player blocked, the server and other clients can't verify that the message was rightfully unacknowledged.

Now, if Mojang on the receiving end of a report checks if the sender was indeed blocked (or the signature invalid and only secure messages shown) you can definitely know whether the reported player maliciously keeps their lastseen signatures empty when checking up the last unacknowledged message (which I hope you do?), but that still means you don't exactly know what they've seen or responded to

Not acknowledging player messages is done with the following client mixin:

@Mixin(ClientPacketListener.class)
public abstract class ClientPacketListenerMixin {

    @ModifyVariable(method = "markMessageAsProcessed", at = @At("HEAD"), argsOnly = true, index = 2)
    public boolean markMessageAsProcessed(final boolean acknowledged) {
        return false;
    }
}