I literally cannot remember if I responded again yet but...
If the self-messages cannot be solved even with label-response or some other means, the echoed messages with other users can at least be identified - the message contains both your own address and the nick of the other person so it can be filtered in that way. Or is that what you were trying to avoid, not stepping on scripts which already deal with that? I suppose they would have to trigger *some* script if the user wanted to change the style of those messages.
So if these use cases can't/won't be solved - can the echo-message support be disabled? And will it be disabled by default?