If you've ever tried to do an instance below or above your level, you know the problem here: the summoning stones outside instances are pretty picky in terms of who they'll summon. This came up for me when a group of us 70s tried to run the Horseman over Hallow's End-- the summoning stone outside Scarlet Monastery wouldn't let us summon each other, claiming we were too high for the instance.
But here's the kicker: Bornakk not only says that there are no plans to change things, but that the reason for not changing them is because Blizzard doesn't want to support higher levels running lower instances, and vice versa. They figure that if you're going to cheat the system like that, you can come up with your own transportation.
But here's the deal: I pay my $15 a month. I should be able to play the game however I'd like. If I want to, as a higher-level character, run my friends through on their lowbie alts (or even solo), as long as it's not actually cheating, I should have the opportunity to do that. Not to mention that, as I said, there are legit reasons to summon people to the stones at those levels anyway-- during holidays, and just as general transportation around the world.
"Because we don't like you doing it" is not a valid reason to have these limits on the summoning stones. If Blizzard really didn't want us running the instances in this way, they'd shut the instances off completely to people outside the level range. Either make it clear you don't want higher levels in there, or get out of our way and let us play the game however we want.