"This modifier to damage is not increased for two-handed weapons, but is not reduced for off-hand weapons."
Does that mean if I wield a katana two handed I don't get my 1-1/2 x Dex Modifier but rather just my dex modifier to damage?
This is assuming I have the Daisho Expertise feat which allows a Katana to be treated as a finessable weapon so long as you're proficient with it, in which case as a two handed weapon it's a martial weapon as oppose to being exotic when it's one handed.
This is for 3rd party content, and I have flagged to be moved to 3rd party forum.
That said yes. When you wield a weapon in two hands, the dex damage is not increased to 1.5 dex.
At the same time, weapons in your off-hand don't suffer from 0.5 dex.
This feat basically encourages you to TWF.