user31586: From the perspective of a full node participant in the network, why is it a bad idea to convey to a peer that a transaction has been rejected because its either a conflict transaction/high fee transaction or a transaction which already known to it? 
I noticed that in the Bitcoin Core source code that REJECT_CONFLICT is set at 0x102 which is greater than REJECT_INTERNAL.
if (state.GetRejectCode() < REJECT_INTERNAL) // Never send AcceptToMemoryPool's internal codes over P2P
    pfrom->PushMessage(NetMsgType::REJECT, strCommand, (unsigned char)state.GetRejectCode(),
                       state.GetRejectReason().substr(0, MAX_REJECT_MESSAGE_LENGTH), inv.hash);

Bitcoin Core code excerpt from src/main.cpp.

user7267: Because it is a waste of bandwidth to convey information that your peers should be calculating themselves anyways. It is also a bad idea to rely on peer's calculations of whether a transaction should be rejected or not because they could be lying to you.

31586: <p>From the perspective of a full node participant in the network, why is it a bad idea to convey to a peer that a transaction has been rejected because its either a conflict transaction/high fee transaction or a transaction which already known to it? </p>

<p>I noticed that in the Bitcoin Core source code that REJECT_CONFLICT is set at 0x102 which is greater than REJECT_INTERNAL.</p>

<pre><code>if (state.GetRejectCode() &lt; REJECT_INTERNAL) // Never send AcceptToMemoryPool's internal codes over P2P
    pfrom-&gt;PushMessage(NetMsgType::REJECT, strCommand, (unsigned char)state.GetRejectCode(),
                       state.GetRejectReason().substr(0, MAX_REJECT_MESSAGE_LENGTH), inv.hash);
</code></pre>

<p>Bitcoin Core code excerpt from <a href="https://github.com/bitcoin/bitcoin/blob/22e0b35676230961aeb848a4f5c6b007cb8a43c9/src/main.cpp#L5142" rel="nofollow">src/main.cpp</a>.</p>
 7267: <p>Because it is a waste of bandwidth to convey information that your peers should be calculating themselves anyways. It is also a bad idea to rely on peer's calculations of whether a transaction should be rejected or not because they could be lying to you.</p>
