I was hunting for a Lavis Cannon and being annoyed that it took 3 hits to kill slimes I grabbed a Gifoie merge to kill em faster, but I had no damage increase.
Damage with nothing on
Damage with a sorcerer cane + Gifoie merge
or is this just some obtuse mechanic I'm not familiar with
Oh that's good to know, I'm surprised I never noticed this before on other versions of the game and it wasn't listed on the Pofuilly/Pouilly page of the wiki.