^Which does not in any way lend credence to the guess that "Class M" had anything to do with Mars. I mean, that's a completely illogical conclusion. If he had intended it to be the initial of a habitable world, obviously he would've gone with "Class E" for Earth.
I disagree. As I mentioned earlier, "Earth-Mars" conditions, abbreviated E-M, pronounced "em", fits quite reasonably. And he very well may have meant not Mars literally, but Mars-sized, barely habitable planets, just to allow wiggle room for worlds that weren't so Terran, such as Korby's planet, Exo III. Or he may have meant Mars, after all, as mentioned above about Spock.
You also seem to be pretty perturbed over this subject. Why's it such a big deal?