Since commenting at the blog requires a noxious log-in, and I know Archade is active on these forums, I'm commenting here instead.
Claim: "The game will break down if you award XP equally to multiple characters run by the same player."
Refutation: "No, it doesn't."
Why would the game break down just because a player can retain more than one character? (What does it mean to "break down" in this regard?) The solution offered is to award XP to the player and not to the character(s), without mentioning the obvious effect: players immediately ditching every character but one. Who wants to play three level two characters when your friend plays a level six character?! (That's what 300 XP gets you)
The solution I prefer, by far: talk to your players. If you all agree the campaign is most fun with three characters each, then give three batches of XP to each player. If you all agree the campaign is most fun with two characters each, then give two batches of XP to each player. If you all prefer one character per player (the way most D&D is played), then give one batch of XP to each player.
In short, give XP to each character, but make sure everybody is on board with the number. Don't ask your players to simply share XP between multiple characters, since that's a recipe for underpowered play in D&D.
If the group is small, or nobody wants to play the Lucky Halfling (or Thief, or Cleric, or whatever), ask one player to volunteer to play a second "semi-NPC" character, or lets call him or her a "cohort", that always trails the party by one level. That is, if the group is level 3, the cohort is level 2. The cohort doesn't need to track XP - it automatically levels when the party does.
PS. In my campaign, all five players maintain three heroes each. On any given adventure, they actively play two of them, with the third one tagging along as a torchbearer and possible replacement. I thus hand out two batches of XP per player.
