Ah. I had interpreted the yellow +/- as "unit is created / destroyed for an unusual reason" (e.g. yellow + = e_unit_buy = unit created by (yellow) gold; so yellow - = e_unit_lost_misc = for instance, because of failure to provide gold upkeep).
A picture saying "we took some damage" seems a bit downbeat to accompany "Your Warriors survived the pathetic attack from the Polish Destroyer". (Perhaps the picture is our advisors' way of communicating effectively despite the triumphalist propaganda that must be used in official reports
) I'm not sure what could be used instead to denote "survival" though... I agree it's better if crossed-swords accompany only active attacks.
I've reverted my changes in the proposed patch for now.