"Mode” is a somewhat fluid term, applying to anything about the method by which the artist accomplishes his aims.-- NOTES TOWARD A SUPERHERO IDIOM.
I'll say up front that Morrison's attitude on the ageing of serial characters is one with which I entirely agree. It remains a study in futility for any fan to attempt to ground serial characters in the real world in terms of how slowly or quickly they age. Umberto Eco touches on some of the narrative consequences of this deathless status quo in his "Myth of Superman," though he doesn't ever quite get to the heart of what makes such a deathless fantasy appealing. However, purely from the standpoint of anyone interested in writing such characters, Morrison's statement shows that the fantasy is clearly one that has strong appeal and that therefore attempts to deal with the anomalies in terms of real-world verisimilitude are doomed to perish of their own fatuity.
Whether or not the "narrarive/subjective" schism between meaning within and meaning without can influence the modes of the combative and subcombative will be seen in future installments of MYTHOS AND MODE.