Ah, if only I were in on that conversation! Genius you may be, Sheldon, but I am the Consistency Theorist!
The discussion (almost an argument) the guys had was over how Superman's suit is claimed. Sheldon said that it's "well established" that to clean his suit, Superman flies into the sun, disintegrating any non-Kryptonian materials. Sheldon also said that the suit itself is made of Kryptonian material. If so, I don't know what continuity that is in.
For instance, in the first issue of the Superman All*Star series, Superman flies to the sun to rescue a science experiment. In this comic, that was Superman's first trip to the sun, which dismisses the idea that he regularly uses the sun to clean his garments. Furthermore, this flight supercharged his cells, tripling his strength to the point that he could die from the overload.
It is well established that Clark Kent's cells are like tiny, ultra powerful solar batteries. He absorbs the power of our yellow sun, and all his abilities come from how the sun works on his cells and physiology.
It is also established, at least in some continuities, that Superman's body is surrounded by a very thin force field, so thin that his skin may feel normal to the touch, but that is what actually gives him his invulnerability. (Well, that, and his incredible healing factor.) When around green Kryptonite, among other things, this bio-electric field goes away.
When in his suit, he somehow, perhaps unconsciously, extends the field a little more. This is what protects the suit. It's also why his cape is often frayed or destroyed, but his suit is not.
Again, I'm not familiar with all the continuities. In some, the suit may actually be made of Kryptonian material, while in others, it's made of regular Earth materials. Again, its protection comes from Clark's extended aura. In issue 1 of Superman All*Star, he actually extends this bio-electric field to protect the sun ship, the Ray Bradbury.
Incidentally, this answers another question: How can Superman, moving super fast, not hurt (nay, destroy) people he has to catch when he rescues them? I have long supposed that he intuitively extends this field around them. Maybe a blob, if you will, of this field goes out at light speed, surrounding the rescuee just before Superman grabs them. His field an their temporary one collide, doing no damage to anyone. Far fetched? No more far fetched than any of his other powers. And realistically, this could be something he's unaware of.
The other issues Sheldon and the boys covered was this: What if Superman sweated on his suit. Would the sweat stains be indestructible? Of course, Superman doesn't sweat on Earth, but let's say he was in the Phantom Zone where he has no powers, got into some brawls, and came out after having worked up a sweat in his suit.
I would argue that only the sloughed-off Kryptonian cells in the sweat would be indestructible. The water, electrolytes, and so on would not be. Therefore, when washing the suit, the stains would come out just like anyone else's sweat. I doubt any cells left behind would make a stain.
I have to also presume that Clark's no-longer-needed cells do die, just like for a human. Otherwise, he would be severely deformed, with huge masses of indestructible cells filling his body.
With the aura theory, the cells would likely not have an aura of their own. Separated from Clark, their power would fade after they died, and they would decompose like normal cells.
So, providing Superman has a good dry cleaner, the sweat stains would prove quite destructible, after all.