Furthermore, the capability is useful for users that have multiple clients attached to a bouncer. 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.
I did somewhat follow the original instructions, except that I connected through znc, used two instances of mIRC instead of one, and used /msg from the status window. I provided this video earlier, it got compressed though so here's a better one: https://giant.gfycat.com/AngelicSelfreliantHammerkop.mp4
But I guess this problem of duplicated text events when targeting yourself is just a specific case of the more general problem that all echoes (to yourself, or other users, or channels) trigger text events at all.
To reiterate the issues when using ZNC with more than one attached client:
1. All echoed queries to other users show up in a query window for $me/$nick instead of a query window for $target.
2. All echoed messages (to any channel or to any user) are now triggering text events.
a. Echoes to other users *can* be distinguished by checking for a difference in $nick and $target
b. Echoes to yourself *cannot* be distinguished from a real message (except by checking that echo-message is enabled then ignoring every other received message, but this sounds fragile)
Problem 2 seems to me rather insurmountable. Users may have scripts which never took into account the possibility of being triggered by their selves and could take some unwanted action. On the other hand, some scripts may want to apply custom formatting to these messages.
So I really don't know what else to say here or suggest, except that no matter what is implemented I hope I can disable the feature as I'm sure it will disrupt my current setup.