James McMurray said:
So given the following two things:
1) Twin spell has a specific rule which states that it duplicates every aspect of a spell (including presumably metamagic).
2) Maximize and Empower have specific rules stating that they do not stack with one another.
You have chosen to believe that Maximize and Empower's specific rule is an exception to the general rule, whereas Twin spell is just stating the general rule.
What makes this any less a house rule than Caliban's position that the oppsite is true, and the Max / Emp is a statement fo the general rule, while Twin Spell is an exception?
Both interpretations are a house rule, because there is no hard and fast rule stating otherwise. It doesn't make either interpretation wrong, but it makes trying to come to a definitive answer in a rules forum fairly difficult.
The fact that Maximize and Empower do not stack with each other:
1. Sets up a general rule that metamgic effects don't stack like that.
2. Does not in any way contradict Twin Spell from functioning on an Empowered (or Maximized, for that matter) spell.
Wipput is right, there are ONLY two ways this can work without contradicting the very plain language in Twin Spell.
1. Both the original and copy of the spell have the extra metamagic feat applied (empower, maximize, whatever)
or
2. Neither the original or copy have the extra metamagic applied.
I find it highly unlikely that you could do a Twin Spell and then be prohibited from using any other metmagic feats on that spell. Still, to make the feat compatible with 3.5, you could simply add in at the end "... when applying Twin Spell to a spell, no other metamgic feats may be used."
The other choice, which I find more reasonable, would be to allow metamagic effects in conjunction with Twin Spell.
I would not call either a "house rule." I'd call them both rules interpretations - not the same thing as House Rules at all.
Caliban's method of applying the Twin Spell effect of repeating the underlying spell only, excluding any metmagic effects is clearly in violation of the plain language of the Twin Spell feat and cannot be considered to be within the rules as written. The feat cannot be rewritten to support this without fundementally chnaging the feat, for the two spells would no longer be identical.
Caliban's method I would definately call a House Rule because it directly contradicts the language in the Twin Spell feat.