Kurald Galain has already addressed all the other points, so I'll just add this one:
If that was what is the case in Dominic Deegan, that would be perfectly fine. We're all for flawed, non-perfect characters. But it isn't. For a flaw to really be a flaw, it must be treated as one, too: People in the universe must react negatively to it. Must point the flaw to the character in question. Must get angry at her/him for it. Mookie, however, does not realise what flaws his characters have himself. Today's strip is a perfect example of that - Luna has just performed an atrocity, yet it is not addressed by anone, and surely never will.
And thus we have supposedly good characters acting in evil ways without falling, reevaluating their ethics or even being questioned by anybody. They are just being praised for their evil deeds. And that is what makes this unrealistic and awfully bad writing.