Okay... not sure whether I should ask this here or in the RotR forum, but figured I'd start here. In the AP, the PCs eventually get the opportunity to make Runeforged weapons.
"... a dominant weapon functions as a bane weapon against transmuters..."
Let's say that hypothetically the weapon already has the Bane (Humanoid [Humans]) property. Would these two stack if used against a Human Transmuter? My initial intuition said yes because it's effectively bane targeting two different aspects shared by the same enemy. Now, I'm not so sure. I'm now leaning more toward no because normally, a bane weapon would only be able to affect any given creature once per attack... I think.
Okay... follow-up question: would bane trigger twice during the same attack if the a single weapon had both Bane (Outsider [Evil]) and Bane (Outsider [Chaotic]) while attacking a Demon for example? I would almost certainly rule no to it stacking in this case, but I'm still unsure about the Runeforged weapon and regular Bane.
There's no rush on solving this. My players are almost certainly at least several weeks from creating a Runeforged weapon (unless the phenomenon our group affectionately refers to "swat team" happens... again), but one of the characters is an Inquisitor, so this is likely going to be an issue at some point.
I'd rule no, along the lines you mention--multiple bane effects don't stack.