Can you take Melee Weapon Mastery twice and have it apply twice to the same weapon?

Question

Can the feat 'Melee Weapon Mastery'

Benefit: When you select this feat, choose bludgeoning, piercing, or slashing. You must have Weapon Focus and Weapon Specialization with a melee weapon that deals this type of damage. When using any melee weapon that has the damage type you selected, you gain a +2 bonus on attack rolls and a +2 bonus on damage rolls. Special: You can select this feat more than once. Each time, you can select a new damage type.

be taken twice and applied twice to a weapon with two different 'types' of damage, such as the morningstar (PHB), which does both piercing and bludgeoning damage?

Example

Feats: Weapon Focus (Morningstar) (+1 to hit with morningstars), Weapon Specialization (Morningstar) (+2 damage with morningstars), GWF (Morningstar) (another +1 to hit with morningstars), GWS (Morningstar) (another +2 to damage with morningstars), Melee Weapon Mastery (Piercing), Melee Weapon Mastery (Bludgeoning), Weapon Supremacy (Morningstar)

From feats alone, before Str, BAB, or other bonuses are added, would this character have

• +6 to hit and +8 to damage (applying both melee weapon masteries to the morningstar as it does both kinds of damage)
• +4 to hit and +6 to damage (applying only one melee weapon mastery feat)
• +2 to hit and +4 to damage (applying no melee weapon masteries)

to attacks made with a morningstar?

Answer 1

No

While it's true that if you have something that buffs a Bludgeoning weapon, and something that buffs a Piercing weapon, this runs into the issue of bonus stacking.

From the basic rules on bonuses:

In most cases, modifiers to a given check or roll stack (combine for a cumulative effect) if they come from different sources and have different types (or no type at all), but do not stack if they have the same type or come from the same source (such as the same spell cast twice in succession). If the modifiers to a particular roll do not stack, only the best bonus and worst penalty applies. Dodge bonuses and circumstance bonuses however, do stack with one another unless otherwise specified.

Emphasis mine. The feat would need to specifically say that the bonus it gives stacks with other versions of the feat on the same weapon. While spells in succession are given as an example, this isn't something that limits it to only spells.

Melee Weapon Mastery gives a bonus to damage with any weapon of the listed type, but you can only get the bonus once per weapon, because for stacking, you only care about the source itself (the feat). It's not a [piercing] or [bludgeoning] bonus, but a [Melee Weapon Mastery] bonus.

If you have Weapon Focus (Morningstar), Weapon Specialization (Morningstar), Melee Weapon Mastery (Piercing), and Melee Weapon Mastery (Bludgeoning), then your attack bonus looks like this:

• +1 to attack rolls from Weapon Focus (Morningstar)
• +2 to damage rolls from Weapon Specialization (Morningstar)
• +2 to attack rolls and damage rolls from the first Melee Weapon Mastery, because Morningstar is of one of the listed damage types.
• The second Melee Weapon Mastery tries to add another +2 to attacks and damage, but sees that [Melee Weapon Mastery] has already been applied to the attack and damage rolls, so it does nothing.

Your overall bonuses with those three feats when attacking with a Morningstar are +3 to attack rolls and +4 to damage rolls.

Answer 2

Officially, No...

The Player's Handbook II errata has the following entry:

Page 81 – Melee Weapon Mastery [Omission]

Add the following the two following sentence to the end of the “Benefit” section: “Weapons with two damage types (such as the morningstar, which does bludgeoning and piercing damage) the benefits of Melee Weapon Mastery (bludgeoning) and Melee Weapon Mastery (piercing) do not stack. But the bonuses from this feat do stack with those gained from Weapon Focus and Weapon Specialization. [sic] (2)

(O, yes, that's an actual cut and paste of what it says. It's readily apparent that 3.5 errata didn't get a lot of love.) While it takes a bit of effort to extract meaning from this word salad, once one does, the two Melee Weapon Mastery feats can't apply to the same weapon simultaneously.

...But a house rule saying Yes would be fine

A fighter who spends his level 8 fighter bonus feat and level 9 level-up feat to become a master with, for example, the morningstar is probably not taking those feats so he can break the game but, instead, so he can, like, claim his place as the greatest morningstarman (?!) in the land or something. That's totally okay.