Here are all the SRD weapon that have special abilities triggered by critical hits. You may note that the language of "successful criticial hit" is not used for Flame Tongue, Mace of Smiting, Nine Lives Stealer or Sword of Life Stealing, thus negating that part of the argument that was postulated early on.
As for the Mace of Smiting making a special exception - maybe so. Of course, that's only implied, and the Sage went even further in declaring that the Improved Critical feat would not apply.
We can only hope they tighten up the language used for Mace of Smiting to fix this problem.
There are two schools of thought on this, really:
(1) Mace of Smiting is special and simply does not follow the rules. Nothing about the Mace of Disruption can be applied to other weapons, because its special.
(2) All special critial effects can occur even if the target is immune to critical hits.
Frankly, number (2) is the far simpler rule, but neither one can really be justified by the rules as written. You have to figure out what is implied by the way the rules were written. This, of course, means that both sides of this argument can easily prevail because the rules simply are written so poorly that you can easily justify either approach.
The Sage's ruling is reasonable except for the Improved Critical exception. For that to be true you have to pull out even more from the Mace of Smiting than exists in the text.
Flaming Burst
Upon command a flaming burst weapon deals +1d6 points of bonus fire damage on a successful hit. In addition it also explodes with flame upon striking a successful critical hit
Icy Burst
Upon command an icy burst weapon deals +1d6 points of bonus cold damage on a successful hit. In addition it also explodes with frost upon striking a successful critical hit
Shocking Burst
Upon command an shocking burst weapon deals +1d6 points of bonus electricity damage on a successful hit. In addition it also explodes with electricity upon striking a successful critical hit
Thundering
A thundering weapon creates a cacophonous roar like thunder upon striking a successful critical hit
Vorpal
This enchantment allows the weapon to sever the heads of those it strikes. Upon a successful critical hit, the weapon severs the opponent’s head (if it has one) from its body
Flame Tongue
This is a +1 flaming burst longsword (+1d6 points of fire damage with each hit, +1d10 points of bonus fire damage on a critical).
Mace of Smiting
This +3 heavy mace has a +5 enhancement bonus against constructs, and any critical hit dealt to a construct completely destroys it (no saving throw). Furthermore, a critical hit dealt to an outsider deals x4 critical damage rather than x2.
Nine Lives Stealer
This longsword always performs as a +2 longsword, but it also has the power to draw the life force from an opponent. It can do this nine times before the ability is lost. At that point, the sword becomes a simple +2 longsword . A critical hit must be dealt for the sword’s death-dealing ability to function
Sword of Life Stealing
This +2 longsword bestows a negative level when it deals a critical hit
Finally:
Critical Hits
When a character makes an attack roll and gets a natural 20, the character hits regardless of the target's AC, and the character has scored a threat. The hit might be a critical hit (or "crit"). To find out if it's a critical hit, the character immediately makes a critical roll — another attack roll with all the same modifiers as the attack roll the character just made. If the critical roll also results in a hit against the target's AC, the character's original hit is a critical hit. If the critical roll is a miss, then the character's hit is just a regular hit.
A critical hit means that the attacker rolls for damage more than once, as indicated by the weapon description for the weapon that scored the threat, with all the attacker's usual bonuses, and add the rolls together to get total damage.
Note that there is NO distinction between a "critical hit" and a "successful critical hit." There is only a "threat" and a "critical hit." The terms "critical hit" and "successful critical hit" are synonomous.
