Comments

The nethack source code has some illuminating and embarrassing comments. Here is a selection, just to get you the feeling.

Illuminating

From pray.c for the function god_zaps_you, about what happens if your god decides to destroy you with a wide-angle disintegration beam but you are disintegration resistant.

/* "I am sometimes shocked by...  the nuns who never take a bath without
* wearing a bathrobe all the time.  When asked why, since no man can see them,
* they reply 'Oh, but you forget the good God'.  Apparently they conceive of
* the Deity as a Peeping Tom, whose omnipotence enables Him to see through
* bathroom walls, but who is foiled by bathrobes." --Bertrand Russell, 1943
* Divine wrath, dungeon walls, and armor follow the same principle.
*/

From the beginning of spell.c explaining how spellcasting penalties work.

/* The roles[] table lists the role-specific values for tuning

* percent_success().
*
* Reasoning:
*   spelbase, spelheal:
*	Arc are aware of magic through historical research
*	Bar abhor magic (Conan finds it "interferes with his animal instincts")
*	Cav are ignorant to magic
*	Hea are very aware of healing magic through medical research
*	Kni are moderately aware of healing from Paladin training
*	Mon use magic to attack and defend in lieu of weapons and armor
*	Pri are very aware of healing magic through theological research
*	Ran avoid magic, preferring to fight unseen and unheard
*	Rog are moderately aware of magic through trickery
*	Sam have limited magical awareness, prefering meditation to conjuring
*	Tou are aware of magic from all the great films they have seen
*	Val have limited magical awareness, prefering fighting
*	Wiz are trained mages
*
*	The arms penalty is lessened for trained fighters Bar, Kni, Ran,
*	Sam, Val -
*	the penalty is its metal interference, not encumbrance.
*	The `spelspec' is a single spell which is fundamentally easier
*	 for that role to cast.
*
*  spelspec, spelsbon:
*	Arc map masters (SPE_MAGIC_MAPPING)
*	Bar fugue/berserker (SPE_HASTE_SELF)
*	Cav born to dig (SPE_DIG)
*	Hea to heal (SPE_CURE_SICKNESS)
*	Kni to turn back evil (SPE_TURN_UNDEAD)
*	Mon to preserve their abilities (SPE_RESTORE_ABILITY)
*	Pri to bless (SPE_REMOVE_CURSE)
*	Ran to hide (SPE_INVISIBILITY)
*	Rog to find loot (SPE_DETECT_TREASURE)
*	Sam to be At One (SPE_CLAIRVOYANCE)
*	Tou to smile (SPE_CHARM_MONSTER)
*	Val control the cold (SPE_CONE_OF_COLD)
*	Wiz all really, but SPE_MAGIC_MISSILE is their party trick
*
*	See percent_success() below for more comments.
*
*  uarmbon, uarmsbon, uarmhbon, uarmgbon, uarmfbon:
*	Fighters find body armour & shield a little less limiting.
*	Headgear, Gauntlets and Footwear are not role-specific (but
*	still have an effect, except helm of brilliance, which is designed
*	to permit magic-use).
*/

Embarrassing

In spell.c function spelleffects, where it creates a stack of 20 spellbooks as a pseudo-objects that it passes to functions that normally expect a scroll or potion.

	pseudo->quan = 20L;			/* do not let useup get it */

In weapon.c function dmgval, when computing bonuses for blessed or silver weapons

	    /* if the weapon is going to get a double damage bonus, adjust
	       this bonus so that effectively it's added after the doubling */
	    if (bonus > 1 && otmp->oartifact && spec_dbon(otmp, mon, 25) >= 25)
		bonus = (bonus + 1) / 2;