Anyways, the PCs are by their very nature special. They are the PCs! The main protagonists! They are the heroes! By their very nature, they defy the conventional limits of normal people to perform exemplary and incredible feats.
Right on!
All PCs can be though of as sharing Power Source: Protagonism. It lets them do all sorts of wondrous things. For starters, it allows them to become to ascend to demigod-like status by killing things and taking their stuff. This doesn't work for normal people. When they try it, they usually 'ascend' to jail or an early grave.
I'm starting to think the best way to conceptualize all this is to bury the notion any D&D class is mundane past a certain level, regardless of whether their hat preference runs toward the pointy (or the miter, or a crown of mistletoe). I'd say 6th or 7th level is a good demarcating line.
I have no problem with high-level fighters flinging mountains or wrestling rivers into a new course. D&D has always trumpeted it's roots in myth and folklore. So it should put its electrum pieces were it's mouth is. Sure, we could introduce Girdles of Mountain-Flinging and Gauntlets of River-Wrestling into the game. Then we'd have an explanation! Everything would be so logical! Whee!
But is that really necessary? Does every epic in-game act require some form of BS materialist/rationalist justification?
Hercules wasn't decked out in a Christmas tree's worth of appropriate magic items when he performed his Labors. Why should a high-level fighter PC. His buddy in the conical hat can make pocket universes.
edit: an example, using Doors (and the 4e concept of Tiers, cause it's handy)
Heroic Tier: a PC fighter has a chance to batter down a heavy door (they are a tough normal person)
Paragon Tier: a PC fighter has a chance to batter down the Door to Moria (they are no longer so normal, more folkloric)
Epic Tier: a PC fighter has a chance to batter down the Gates of Hell (epic, like it says on the tin).