Necroequipugilism
OK...covering a lot of ground in this one (apologies in advance if something comes out disjointed):
Various consolidated relevant quotes from the PHB, DMG, & SRD mostly from various posts in the old Flaming Whip thread (some original quoters gave no page info)
1) PHB: When you make an attack roll, you roll a d20 and add your attack bonus.<snip>If your result equals or beats the target’s Armor Class, you hit and deal damage.
2) PHB: "When your attack succeeds, you deal damage...<snip>Damage reduces a target's current hit points."
3) SRD: Upon command, a flaming weapon is sheathed in fire. The fire does not harm the wielder. The effect remains until another command is given. A flaming weapon deals an extra 1d6 points of fire damage on a successful hit. Bows, crossbows, and slings so crafted bestow the fire energy upon their ammunition.
4) From the 3.5 FAQ (page 55): a fighter wielding a +1 flaming sword can’t choose for the fire damage to be nonlethal (even if the base weapon damage is nonlethal)
5) DMG p28: Certain types of damage, however, should never be nonlethal damage...such as fire
6) PHB p136:
Touch Attacks Some attacks disregard armor, including shield and natural armor.
7) PHB: Dealing Nonlethal Damage," which reads, in part: You can use a melee weapon that deals lethal damage to deal nonlethal damage instead, but you take a -4 penalty on your attack roll because you have to use the flat of the blade, strike at nonvital areas, or check your swing.
The above all quoted in no particular order to support the following (also in no particular order):
Several of the quotes essentially state that damage is the consequence of a successful hit. Indeed, going by the combat rules alone,
damage is the only possible consequence of a successful hit.
Me, in that Flaming Whip thread
When your attack succeeds, you deal damage. (Rule)
Damage reduces a target's current hit points. (Lemma)
A successful trip attack results in the target being tripped.
Nowhere in the trip attack rules (PHBp158) does it state that a trip attack does or doesn't do damage... so either trips do normal damage for the method in which the trip is delivered OR (see Conclusion below).
...
So we have a conundrum.
Conclusion- Either not all successful attacks deal damage- contradicting the very first Rule under the Dealing damage section, and thus the RAW- or the Lemma is false, also contradicting the RAW.
My way around this conundrum:
Me, in that Flaming Whip thread
The NATURE of the damage may vary- it may be regular damage like a sword-blow, non-lethal like a stunning fist, it may be insta-kill like a Vorpal beheading, it may even be a special effect substituted for damage like a trip- but RAW (

)- the result of a successful attack roll is damage.
Now, most people
assume that a trip attack does not do damage, I among them. The reason is twofold:
1) If you successfully trip your opponent, he falls prone- this is the only result. The specific rules section does not mention dealing damage as the result of a successful trip attack.
2) If you have Improved Trip, you immediately get a melee attack against that opponent (as if you had not used the successful attack to Trip), presumably to do damage while he is prone. That would mean that with the feat, you'd get to Trip + Do damage + Attack again to do damage- a formulation most would probably consider overpowered.
Besides, we have other kinds of post-attack effects- some even referring to "damage" other than reduction of hit points- like attacks that damage (reduce) ability scores, grapples get initiated, targets get tripped...or affected by a variety of spells. In other words, "damage" != reduction of hit points. They may
say it does, but they clearly don't use the word with any real precision. "Damage" is just their semi-efficient codeword for "the weapon (or other attack) has its stated effect."
Re #6 & 7:
Now, while it is true that the rules do not explicitly state that you can make a "touch attack" with a melee weapon, neither do the rules specifically EXCLUDE making touch attacks with melee weapons. See #6 above- that section tells you the mechanics, and even gives two examples based upon a wizard using Shocking Grasp- but it does not even start to delineate what is and what is not capable of being used for such an attack. That is left open.
Similarly, #7 above notes that there is at least one other way to use a normal weapon- dealing non-lethal damage.
So, since its not explicitly excluded, it is up to your DM to rule whether you can make a touch attack with a melee weapon. IMHO, its completely fair since it would at least reflect the custom of "counting coup"- the practice of striking an opponent in melee, but without intention to do damage, only to touch them in an exposed area, as a measure of a warrior's bravery & skill...and mercy. Since it is a successful strike in melee, such a strike should trigger the bonus damage from a weapon such as we've been discussing. (Of course, one could argue that using such a weapon to count coup violates the spirit of the practice, and a warropr should not be credited with coup using such a weapon...but the fire still gets triggered.)
Re #3 & 4 above:
Me, in that Flaming Whip thread
It seems to me, and to others, that the reading of the Flaming power is being tortured. Some feel that the damage is being done by the weapon, not the enchantment. "A flaming weapon deals..." has been much discussed, but read on.
The second sentence of this entry reads "THE FIRE does not harm the wielder"- not "THE FLAMING WEAPON." This matters. They have already made a distinction between the weapon and the power granted by the magic. "A flaming weapon" is nothing more than a description of a weapon wrapped in a shroud of magical fire.
Me, in that Flaming Whip thread
Lets assume that the game's writers are rational human beings, the statement:
The fire does not harm the wielder.
must have a rational meaning.
1) They mentioned that the Fire doesn't hurt the wielder for a reason.
2) The reason is to point it out as an exception to the general rule that fire burns those in contact with it.
3) That the class of persons not burned by the fire on the weapon is limited to a single class- the "Set of People Wielding the Firey weapon" would indicate that persons OUTSIDE that class are not immune to damage by the fire.
and, in the context of the sentence immediately precedent to which it refers:
Quote:
... a flaming weapon is sheathed in fire.
4) The fire damage that would normally be done to the wielder comes from the fire enchantment- not the weapon.
And #4 specifically states that he cannot make the FIRE portion of his damage non-lethal (an option he has with the blade of his weapon). It distinguishes between what is doing the damage- some is the weapon, not the fire, the other is the fire, not the weapon.