delericho
Legend
Hah, yeah - but the issues come into play when (1) he's a 10th-level commoner,
I deal with that by ruling that normal (as in non-adventurer) characters don't get above 5th level. No way, no how. That 20th level Commoner (or even the 10th level one) is a theoretical construct - he doesn't exist IMC. (Excepting something like Berem from Dragonlance, but he's inherently a special case.)
(2) your jewelers, architects, and musicians are beating your equally-experienced farmers in brawls
That's fair... mostly. The Commoner NPC class is clearly weaker than any of the others. If I was actually concerned about balance, I would give a Commoner one more level than an 'equivalent' Expert or Warrior.
Not being particularly bothered with balancing the NPC classes, I'll instead note that the difference (at 5th level) is +1 BAB, +3 Will save, and +6 hp (on average). Incidentally, both my sample commoner and the +6 value I've just given assume max hit points at 1st level.
So the expert mostly wins, but even at 5th level it's not a huge disparity. If I really wanted to give an in-world justification, I'd say the Expert gets a better diet by virtue of improved wealth (for having a saleable trade). But I'll readily accept that that's a stretch.

(3) you compare that 5th-level commoner to a standard 1st-level town guard in leather with a spear truncheon.
Well, three things about that:
1) Why is the warrior using substandard weapons and armour? Surely he should be using appropriate gear, or it's not a fair comparison?
2) We're comparing the most extreme outlier amongst farmers with the run-of-the-mill warrior. I'm not sure I have a problem with the Commoner winning in those circumstances.
3) In any case...
Bob, Joe's Warrior Cousin
1st level Warrior
Str 13, Dex 10, Con 12, Int 9, Wis 11, Cha 8
Skills: Intimidate +3
Feats: Weapon Proficiency (simple, martial), Armour Prof (all), Shield Prof, Weapon Focus (longsword), Toughness
Hit Points: 12
AC: 16 (scale mail, large shield)
Fort +3, Ref +0, Will +0
Attack: Longsword +3, 1d8+1 damage
Attack: Light Mace (thrown) +1, 1d6+1 damage
I'm not sure that Joe would win that fight - yes, he has quite a few more hit points, but he's also considerably less likely to hit. I suspect it would be a close run thing. Where Joe is better is in his chosen skills, where he roundly outclasses Bob... but that's as it should be.
(Amusingly, I've now written far more words than I intended in defence of something that I file under "more trouble than it's worth".
