The spec suggests ZNC should be sending the echo to all clients, "In this scenario, when users send messages from one client, the messages get automatically relayed to other attached clients. This allows all attached clients to display full conversation." This makes sense for conversations with other users, and I believe that echo should not trigger text events. It does make a little less sense for conversations with yourself though.

And although echo-message says it addresses self-targeted message limitations in the labeled-response doc, I do not see that addressed and I still do not understand how mIRC could differentiate between sent message and its echo.